A. SOME IMPORTANT TERMS
"Najasat" (pl. najasat) means uncleanliness, impurity.
In Islamic laws, the najasat is of two types: inherent and acquired. To differentiate between the two, a thing which is inherently unclean is known as "`ayn najis," whereas a thing whose uncleanliness is acquired is known as "najis". A pure thing acquires impurity by coming into contact with one of the `ayn najis. For example: blood is considered an `ayn najis, whereas milk is considered pure. Now, if a drop of blood falls into a glass of milk, the milk will become najis because of the blood which is an `ayn najis.
The plural of `ayn najis is "a`yan najisah."
"Taharat" is opposite of "najasat," it means cleanliness and purity.
"Tahir" is opposite of "najis," it means a thing which is clean and pure.
B. THE A`YAN NAJISAH
(THE INHERENTLY UNCLEAN THINGS)
According to the Islamic laws, the a`yan najisah are nine in number. The nine a`yan najisah can be divided into four groups as follows:
i. Common between Men & Animal:
ii. In Animals only:
iii. In Man only:
9. intoxicating liquids.
The implication of this law for a Muslim is that he or she must refrain from the a`ya najisah in three things: acts of worship, food and drink.
In the following pages, we shall explain the rules regarding the nine inherently impure things.
1. & 2. URINE AND STOOL
The urine and stool of human beings are `ayn najis.
Most people of the world consider urine and stool as unclean, but Islam has gone one step further in declaring them to be ritually unclean. For example, in the matters of worship a Muslim who has passed urine or emptied his bwels cannot pray even after cleaning his body from urine and stool-he must also do wudu, a minor ablution which will be discussed in chapter 2.
The Islamic shari'ah has prescribed certain rules on how to cleanse oneself of urine and stool.
1. The organ of urination can be made tahir only by the pouring of water on it at least twice. It is better to wash it three times.
2. As far as the anus is concerned, a person can clean himself/herself with water, or with three pieces of papers, or three pieces of rags or three stones. The papers, rags and stones can be used only if the anus is not more than normally dirtied, i.e., the excrement has not spread more than normal. If the area dirtied is large, or the excrement is mixed with some other najasat like blood, then only water can be used to purify oneself.
However, it is always better to wash oneself with water. While praising the people who built Masjid Quba, Allah says, "Therein are men who love to cleanse themselves; and Allah loves those who cleanse themselves." (9:108) When this verse was revealed, the Prophet asked the people of Quba, "What do you do when cleaning yourselves that Allah has praised you for it?" They said, "We cleanse ourselves after emptying the bowels with water." 
3. In case of cleaning oneself with three pieces of papers, rags or stones, it is obligatory to use all the three pieces even if the body becomes clean by one or two of them. However, if the body is not clean even after using the three pieces, then extra pieces must be used till the body becomes clean.
4. It is recommended for men to do istibra' after urinating. Istibra' means to clean something, to get rid of something. Here it means getting rid of the remaining drops of urine from penis. The method of istibra': Squeeze with the middle-finger of the left hand from the anus to the root of the penis three times; then holding the penis between the thumb and the fore-finger, squeeze three times from the root up to the glans; and squeeze the glans itself three times.
The benefit of istibra': If a liquid comes out of a man's penis after urinating and he doubts whether this is urine or something else, then he can assume it to be tahir if he has done istibra'. But if he has not done istibra', then he must consider it najis.
5. In western toilets, there is no water, only tissue paper is available. As far as stool is concerned, it can be cleaned with tissue paper as explained above. In case of urinating, would it be enough to wipe the related part with tissue paper? No, wiping with tissue paper would not purify the organ of urination. Nonetheless, in such a case, one should do istibra' and then wipe the organ with tissue paper, and later on when it becomes possible, he or she must purify the organ with water. The benefit of istibra' and wiping with tissue paper is that the organ will become dry and not make the underwear or the thighs najis.
However, in the above case, if the person's private parts sweat, then he or she must purify the organ, the immediately surrounding area and the underwear with water. `Ays bin al-Qasim asked Imam Ja'far as-Sadiq (as) about a person who urinated in a place where there was no water and so he dried his penis with a stone, but later he started sweating in the same area. The Imam said, "He should wash his penis and thighs." 
6. While urinating or emptying the bowels, it is necessary to conceal one's private parts from the on-lookers. This condition is easily taken care of in normal toilets, but one must be careful while on the call of nature in an open area, e.g., during a picnic or while travelling, etc.
7. A Muslim should also realize that even for such a trivial thing as using toilet, Islam emphasizes that either you must be the owner of the washroom or you must have the permission of the owner; otherwise, it will be haram for you to fulfill your natural needs in that place.
8. It is haram to face the qiblah or to keep the qiblah on the back side while urinating or evacuating the bowels. Qiblah means the direction of the Ka'bah (Mecca). Therefore, a Muslim must make sure that the toilet of his house is not built in such a way that when he sits on the toilet, his front or back side is towards the qiblah. If the circumstances make it necessary to use a toilet on which a person will either be facing the qiblah or will have his back towards it, then he should refrain from facing the qiblah.
* * *
The urine and excrement of the animals are also najis if they belong to the group of animals (1) whose meat is forbidden in Islam and (2) whose blood spurts out when a blood-vessel is cut. Therefore, if these two conditions are not found together in an animal, its urine and excrement are not najis. For example, even though its blood spurts out, sheep's urine and stool are not najis because it's meat is not forbidden.
However, the droppings of all the birds are tahir.
What should a person do if he finds animal stool or excrement on his dress or person and doesn't know from which type of animal it originated? In all the cases of ignorance and doubt, one can assume that it came from an animal whose urine or excrement is tahir.
Abu Agharr an-Nahhas, a veterinarian, said to Imam Ja'far as-Sadiq (as): "I treat the animals. Sometimes I have to go (to treat them) at night. The animal may have urinated and emptied its bowels; and when it jumps on its own refuse and urine, it splashes on my dress. Then in the morning, I see its trace on my dress. [What should I do?]" The Imam said, "There is nothing on you."  This answer can be explained in two ways: Abu Agharr could assume that his dress was still pure because in the darkness of night he could not have been sure of what come on his dress, or because the animals were domesticated and thus their refuse and urine is not najis.
Semen is also one of the `ayn najis.
There are many ahadith on this issue, but here I will just describe a historical event and its relevant Qur'anic verse which proves that semen is najis.
In the battle of Badr, the unbelievers of Mecca had camped near the spring of Badr and the ground of their camp-site was firm. On the other hand, the Muslims were far from the spring and thus experienced difficulty in getting water; and the ground under them was sandy which made their stand and manoeuvres difficult. To make the matters worse, many of the Muslims had nocturnal discharge in their sleep and became impure (najis). Then came Allah's help which the Qur'an describes as follows:
And (remember) when He spread a cover of drowsiness over you as a security from Him (and thus you slept peacefully). And He sent down upon you water from heaven to purify you with it, to take away from you the unclean (insinuation) of the Shaytan, to strengthen your hearts and to plant you feet firmly with it. (8:11)
The words relevant to our subject are: "He sent down upon you water from heaven to purify you with it." The least that this verse proves is that semen is najis, and with its discharge a man becomes ritually impure.
`Abdullah ibn Abi Ya'fur asked Imam Ja'far as-Sadiq (as) about a dress which had come into contact with semen. The Imam said, "If you know the particular part of the dress which came into contact with semen, then wash that area only; but if that part is unknown to you, then wash the whole dress." 
* * *
Sometimes a liquid, other then semen and urine, is discharged from man; this type of liquid is not najis. These liquids are of three types:
1. Mazi: a whitish liquid which is discharged from penis during sexual fore-play.
2. Wazi: a liquid which comes out after the discharge of semen.
3. Wadi: a liquid which comes out after urinating.
All these discharges are tahir.
Blood of human being is najis.
Blood of the animals whose blood spurts out is also considered najis. But the blood of an animal whose blood does not spurt out is tahir, e.g., the blood of fish or the body-fluid of a mosquito. Ibn Abi Yafur asked Imam Ja'far as-Sadiq (as), "What do you say about the blood of fleas?" The Imam said, "There is no objection in it." Ibn Abi Ya'fur, "Even if it is more and excessive?" The Imam, "Yes, even if it is more." 
After an animal has been slaughtered and the normal amount of its blood has flowed out, the blood remaining in its body is tahir.
The blood found in an egg is also najis.
If there is blood on someone's dress or on his person and he doubts whether it is of an animal whose blood spurts out or not, then he should consider it tahir.
If a yellowish liquid comes out of a wound and one doubts whether it is blood or something else, then he should consider it tahir.
Even though blood is considered najis, one is still permitted to donate or sell his blood. Doctors, nurses, and scientists can work and experiment with blood. The only important thing is that at the time of praying, one's body and dress must be free from this najasat.
The dead body of a Muslim becomes najis after becoming cold and before being washed (ghusl mayyit).
al-Halabi asked Imam Ja'far as-Sadiq (as) about a person whose dress had fallen upon the body of a dead human being. The Imam said, "If the dead body had been given the ritual bath (ghusl mayyit), then there is no need to wash your dress which touched it; but if the body had not been given the ritual bath, then wash whatever part of your dress that had touched it." 
A kafir is najis both during his life-time and after his death.
If a part of a living human being's body or of a living animal's body is cut off, it will be considered najis. This law, however, does not apply to the dry skin which comes off the lips or the skin which comes off from a healing wound, or pimples, dandruff, etc.
A miscarried fetus is also najis.
* * *
"Dead body-maytah" in case of the animals means: an animal which had died naturally or was slaughtered in a non-Islamic way.
The dead body of an animal whose blood spurts out is also najis with the exception of those of its parts which have no life (feeling) in them during life-time, e.g., hair, nails, bones, beak, horn and teeth. Of course, these parts become najis by being in contact with the dead body; so after separating them from the animal's body they must be purified.
The dead body of the animal whose blood does not spurt out is tahir; for example, a dead fish. `Amman as-Sabati says that Imam Ja'far as-Sadiq was asked about a beetle, a fly, a locust, an ant and other similar things that die in a well, oil, butter or other such things: The Imam answered, "There is no objection concerning all (the animals) that do not have (spurting) blood." 
If someone buys a dress, a belt, or a wallet, etc, made of an animal's skin and does not know for sure whether or not the animal was slaughtered Islamically, then in such a case there are two possibilities:
1. Either he has bought it from a Muslim or from a Muslim market, then he can assume that the animal was slaughtered according to the shari'ah.
2. Or he has bought it from a kafir. In such a case if there is a probability that the skin or hide has been taken from an animal which was slaughtered according to the shari'ah, then he can consider it tahir and use it. However, he still cannot use such a thing in salat (prayers). And if there is no such probability, then he cannot consider it tahir, it should be regarded as najis.
6. & 7. PIGS AND DOGS
Pigs and dogs are also counted as `ayn najis.
Allah says in the Qur'an: (O Muhammad) say, "I do not find in what is revealed to me anything forbidden for a person to eat except (1) what has died of itself, (2) outpoured blood, (3) the flesh of pig --for it is unclean and (4) an ungodly thing (i.e., the animal) slaughtered (with the name) of other than Allah" (6:146)
Although this verse is related to the forbidden food, but it clearly defines the pig as an unclean animal. Khayran al-Khadim wrote to Imam 'Ali an-Naqi (as) asking about a dress which had come into contact with intoxicating liquid and flesh of pig: "can a person pray in that dress? Our companions had different opinions: some say you can pray in it because Allah has only forbidden the drinking of the intoxicants, while others say you cannot pray in it." The Imam answered, "Do not pray in that dress because it is najis." 
Abu Sahl al-Qarshi asked Imam Ja'far as-Sadiq (as) about the dog: "Is the dog haram?" The Imam said, "It is najis." Abu Sahl repeated this question three times and the Imam always replied, "It is najis." 
Based on such teachings, our mujtahids have ruled that all parts of pigs and dogs, even the nails, hair, teeth and bones, and their saliva, milk, urine and excrement are najis. Therefore, all things made from pig's fat, skin, hair, and other parts of its body (e.g., belt, gloves, jackets, and shoes) are najis. Similarly, all the food items produced from the meat and fat of pig is najis.
8. THE KAFIRS
What is the meaning of "kafir?" Kafir (pl. kuffar) means an infidel, an unbeliever as opposed to a Muslim, a believer. "Muslim" is defined as a person who believes in Oneness of God, prophethood of Prophet Muhammad, and the day of judgement. A person who rejects any of these three principles is a kafir.
From Muslims' perspective, the kuffar are divided into two main groups: kafir dhimmi and kaf'ir harbi. "Kafir dhimmi" is a kafir who lives under the protection of an Islamic government. "Kafir harbi" is a kafir who does not have such a protection. I must also mention a third, but rare, category of kafir: murtad. "Murtad" means an apostate; there are two types of murtad: "Murtad fitri" a person who was born of a Muslim parent, but then declared his disbelief in Islam. "Murtad milli" a non Muslim who had accepted the religion of Islam and then apostates from it.
* * *
While discussing the ritual purity or impurity of the non-Muslims, the mujtahids divide all the kuffar--dhimmi, harbi, murtad fitri and milli-into two distinct groups: mushrik and ahlu '1-kitab.
Mushrik (pl. mushrikin) means a polytheist, a person who believes that God has partner(s). It is used for the idol-worshippers also. The followers of Hinduism, of most far eastern religions and of the tribal religions fall in the category of mushrikin. Ahlu ' l-kitab means the people of the Book; it is a name given to those who believe in any of the Books revealed by Allah before the Qur'an. Under Islamic system, the Ahlu '1-kitab have a preferred status in comparison to other non-Muslims. The people who are unanimously counted as Ahlu '1-kitab are: the Jews, the Christians and the Zoroastrians.
As for the mushrikfn, the mujtahids are unanimous that they are najis. This is so because Allah has clearly declared in the Qur'an that: "O you who believe! The polytheists (mushrikun) are indeed unclean; therefore, they should not approach the Sacred Mosque after this year of theirs (i.e., 9 AH)." (9:28) Some Muslims try to interpret the word "unclean" in spiritual sense only. They are wrong because one cannot ignore the literal meaning of a word unless the context supports the departure from a literal to a symbolic meaning. The context of the verse does not leave any room for an exclusively symbolic or spiritual interpretation of the word "unclean." It immediately says that "they should not approach the Sacred Mosque." This reflects the physical uncleanliness. However, our interpretation does not exclude the spiritual impurity of the mushrikin along side the physical, ritual impurity.
* * *
When we move on to the Ahlu ' 1-kitab, we find that the mujtahids disagree about their ritual purity or impurity. There are three different views on the Ahlu 1-kitab. (1) A minority group says that the Ahlu '1-kitab are pure and tahir, just like Muslims. To this group belong the late Ayatullah al-`uzma Sayyid Muhsin al-Hakim at Tabataba'i (d. 1970) and the late Ayatullah ash-Shahid Sayyid Muhammad Baqir as-Sadr (d. 1980).  (2) The majority view says that the Ahlu '1-kitab have become corrupt in their beliefs and are not different from mushrikin; therefore, they are najis. Those who belong to this group from the present mujtahids are: Ayatullah al-`uzma Sayyid Ruhullah al-Musawi al-Khumayni and Ayatullah al-`uzma Sayyid Muhammad Riza alGulpaygani.  (3) The third group is of those mujtahids who theoretically agree with the first view but when it comes to issuing a fatwa for their followers, they tread on the path of precaution and side with the majority. The most prominent among this group is the Ayatullah al`uzma Sayyid Abu '1-Qasim al-Musawi al-Khu'i.
Ayatullah al-Khu'i, in his lectures on fiqh, says: "It is apparent from what we have discussed above that the purity (taharat) of the Ahlu '1-kitab was taken for granted by the narrators of hadith till the end of the era of our Imams [i. e., till the minor occultation], and whatever they asked the Imams concerning the works of the Ahlu '1kitab was just because of the doubts they had about external najasat which might have affected them.
"Therefore, it is difficult to give a fatwa on basis of the ahadith which apparently say that the Ahlu '1-kitab are najis; however, on the other hand, to gave a ruling on basis of the ahadith which say that they are tahir is even more difficult because the majority of our jurist companions, both from the early days and the later days, believe in the najasat of Ahlu '1-kitab. And so there is no escape from a binding precautionary measure on this issue."  And therefore we see that while issuing the fatwa for his followers, Ayatullah al-Khu'i writes, "As for the kiadbi (kafir), the famous view says that he is najis; and it is precautionarily necessary (to consider him as such)." 
With all due respect to the great marja ' of our time, I would just repeat what the famous mujtahid of the 10th Islamic century, ash-Shahid ath-Thani Shaykh Zaynu'd Din al-`Amili, said on this issue: "To act in contradiction to the majority view is difficult but to agree to their view without any convincing proof is even more difficult." 
Irrespective of the view to which I am inclined, the reader is advised to follow the opinion of his own mujtahid on this issue.
* * *
There are three other groups -ghulat, nawasib, and khawarij- who are also considered kafir and najis by the Shi`ah fiqh, in spite of the fact that these groups were off shoots of Muslims during the early stage of the Islamic history.
Ghulat (s. ghali) are those who declare their faith in Islam but exaggerate in their beliefs about some prophets or Imams, e.g., those who believe that an Imam is an incarnation of God. This is against the fundamental belief of Islam that God cannot incarnate into anyone or anything.
Nawasib (s. nasibi) are those who declare their faith in Islam but display enmity toward the Ahlu'1-bayt (peace be upon them). This goes completely against the Qur'anic order which says, "(O Muhammad) say, `I do not ask from you any reward for it (i.e., conveying the message) except the love for my near ones." (42:23) The Prophet has said, "Whosoever dies in enmity to the family of Muhammad, dies as an unbeliever (kafir). Whosoever dies in enmity to the family of Muhammad, will not smell the scent of Paradise."  However, one must realize that if a person is not a Shi'ah Muslim it does not automatically follow that he also hates our Imams. There are many Sunnis who do not believe in our Imams as the leaders and the caliphs after the Prophet, but neither do they hate them---on the contrary many of them respect and even love the Imams of the Ahlu '1-bayt.
Khawarij (s. khariji) are those who rebelled against Imam 'Ali bin Abi Talib in the battle of Siffin. Finally, Imam 'Ali had to fight against them in the battle known as Naharwan. They believed that Imam 'Ali had become a kafir by accepting the intermediaries during the battle against Mu`awiyah. The verse and the hadith mentioned above is equally applicable to the khawarij, and therefore, they are also kafir and najis.
There is one more category of a kafir. The person who rejects the unanimously accepted tenets of Islam (for example, the obligation of salat or haj), is also regarded as a kafir and najis. Such a person will become kafir provided he realizes that rejecting such Islamic tenets amounts to believing that the Qur'anic verses on salat and hajj are not part of Allah's Book, and this in turn means that Prophet Muhammad had not been faithful in fulfilling the mission of Allah. In short, such a person becomes a kafir only if he realizes the consequence of his rejection of the unanimously accepted tenets of Islam. However, one must note that negligence and rejection are two different things; so if a person believes in the unanimously accepted tenets of Islam but neglects them, he is not a kafir, he is only a sinner.
9. INTOXICATING LIQUIDS
Every intoxicating liquid is najis.
Allah says in the Qur'an: "O you who believe! Surely intoxicants, games of chance, idols and azlam are unclean (and) work of Shaytan, so shun it; may be you will prosper." (5:90) The word "unclean" in this verse, at least as far as the intoxicants are concerned, has a spiritual as well as a ritual connotation to it. And ritual uncleanliness is another word for najis. Moreover, the answer of Imam 'Ali an-Naqi (a, s.) to Khayran's letter quoted earlier clearly says that intoxicants are not just haram but also najis.
Beer is also najis. But all non-intoxicating drink made from barley are tahir.
The non-liquid intoxicants are haram (forbidden) but not najis. Methyl alcohol (also known as wood alcohol or wood spirit) is tahir; it is mostly used for industrial solvents, and for making synthetic rubber, chemicals, rubbing alcohol, inks, dyes and stains, antifreeze and other similar products.
C. SOME GENERAL RULES
Buying or selling the following najasat is haram: all types of intoxicating liquids, dead bodies, pigs and dogs (except the dogs used for hunting).
However, one is allowed to buy or sell the other najasat if there is any lawful benefit in them, e.g., buying or selling excrement for manuring. It is also permitted to buy or sell those parts of a dead animal's body (other than dog and pig) which have no feeling in them during life-time. It is haram to sell grapes or dates to a person who purchases it for producing wine.
If a clean (tahir) thing comes into contact with any of the najasat, then it will not become najis unless one of those two things was wet.
The medicines, perfumes, soap and waxes purchased from a non-Muslim country can be considered tahir unless one becomes sure that they are najis.
D. THE MUTAHHIRAT
(THE PURIFYING AGENTS)
What you have read above was about a`yan najisah, the ten inherently unclean things. You also came to know that other things can become ritually impure (najis) by coming into contact with one of the ten a'yan najisah.
Is it possible to purify the najis things? Yes. We can purify a thing which has become najis by coming into contact with the one of the a'yan najisah. Is it possible to purify the a `ayan najisah? Some a'yan najisah can be purified easily, while other a'yan najisah can be purified only through a long process of change and transformation. The function of purifying such things is done by the mutahhirat.
Mutahhirat is plural of mutahhir. It means a thing or a process which can ritually purify the najis things and the a'yan najisah. "Mutahhirat" can be translated into English as "the purifying agents." The mutahhirat are eleven in number. These mutahhirat can be divided into three groups:
i. The Nature:
2. the earth;
3. the sun;
ii. Physical Change:
4. istihalah (chemical change);
5. inqilab (change in properties);
6. intiqal (change in place);
7. zawalulI-`ayni n-najasah (disappearance of the najasat);
8. istibra' (quarantining);
iii. Spiritual Change:
10. taba`iyyah (to follow);
11. ghaybatu ' 1-muslim (disappearance of a Muslim).
Not all of these mutahhirat can purify every najis or every `ayn najis thing. Only water is the most universal purifying agent, whereas other mutahhirat are very limited in scope. In the following pages we shall explain the rules about these eleven mutahhirat.
First among the mutahhirat is water. The Qur'an says:
"He (Allah) is the one who sends the winds as good news before His mercy; and We send down pure water from the cloud." (25:48) Water is indeed the most common and widely used purifying agent. However, the way water can purify a najis thing depends on its type and quantity. So first we will describe the various types of water and then explain the rules of purification.
* * *
According to the shari'ah, water can be of two types: mutlaq and muzaf.
Mutlaq means pure water, a water which is not mixed with any other liquid. When we use the term pure, in the present context, we do not mean scientifically pure water, i.e., H20, a liquid compound consisting of 2 part of hydrogen and 16 of oxygen. By mutlaq we mean a water which people in general would consider pure, without putting it to a scientific test.
Muzaf is opposite of mutlaq, it means a water which is mixed with some other liquid, e.g., orange juice, tea.
For the purpose of purifying a najis thing, only the mutlaq water can be used. Therefore, muzaf water is not one of the mutahhirat.
The mutlaq water can be found in five different forms:
2. Well water.
3. Running or flowing water, e.g., river, stream. The water running from the pipes in the houses is treated as `running water' as long as it is running.
4. Kur water: a body of water which is still (not moving). It must be at least 377 k.g. in weight, or must occupy at least 27 cubic span space. Examples of kur water: a swimming pool, a pond, a lake, a sea or an ocean.
5. Less than kur. A body of still water which is less than the kur.
The first four types of pure water are known as Kathir water, and the last one is known as qalil water. Kathir means abundant or plentiful; qalil means less.
Water can make a najis thing tahir on the following conditions:
1. it must be mutlaq;
2. it must be tahir;
3. it must not become muzaf by coming in contact with the najasat;
4. the najasat must be washed away from the najis thing.
* * *
Because of its quantity, the Kathir water is immune from becoming najis by contact with a najasat except when the najasat is so strong or so much that it changes the taste, or the colour or the smell of the water. When cleaning a najis thing with the Kathir water, it is enough to wash it just once after removing the najasat.
Unlike the Kathir water, qalil water becomes najis as soon as it comes into contact with a najasat. When cleaning a najis thing with qalil water, it is necessary to wash it twice. However, it is better to wash three times.
Almost all solid things that become najis can be purified by washing once with Kathir water or twice with qalil water. Examples of solid things: clothes and shoes, curtains and sofas, carpets and furnitures, fruits and vegetables, utensils and pots.
However, there are a few things which have to be washed in a different way
1. A piece of cloth that has become najis by urine must be washed once in running water or twice with other types of water, and it must also be squeezed after each wash.
2. A pot licked by a dog must be rubbed with wet and clean earth thoroughly; then, after washing away the earth, it must be washed once with Kathir water or twice with qalil water.
3. A pot that has become najis by intoxicating liquid must be washed three times with Kathir or qalil water; however, it is better to wash it seven times.
4. A pot licked by a pig must be washed seven times with Kathir or qalil water.
As for the liquid things that may become najis (e.g, milk), they cannot be purified with water. The only possible way for purifying a najis liquid is its complete transformation or change-the purifying methods which will be discussed later on.
2. THE EARTH
The second among mutahhirat is the earth.
However, the earth is not a universal purifying agent like water. It's purifying scope is very limited. It can only purify the sole of the shoes and the sole of the feet provided:
1. the shoe or the foot had become najis by a najasat on the earth;
2. the najis element is removed from the soles by walking on the earth;
3. the earth is dry and tahir.
3. THE SUN
The sun is the third and last among "the natural mutahhirat."
The sun is also a limited mutahhir like the earth. It can purify only the following things that become najis: 'the earth and all the immovable things on the earth like trees, the fruits on the trees, the grass. It can also purify the immovable things of a house like walls and doors.
The sun can purify the above mentioned things provided:
1.the najasat has been removed;
2. the najis place or thing is wet. So if a najis place or thing has become dry and you wish to purify it by the sun, then you will have to pour water on it and let it dry up by direct rays of the sun.
3. the najis thing or place must become dry by the direct rays of the sun.
Istihalah is the fourth mutahhirat. Istihalah means change or more precisely, a chemical change. It is the most universal mutahhirat in the category of `physical change'.
An `ayn najis or a najis thing can become tahir by changing chemically into another tahir thing.
A few examples of an `ayn najis changing into a tahir thing: Urine evaporates, becomes steam and then changes into liquid form. A dog's body changes into earth. A pig's body thrown into a salt mine changes into salt. The manure made from the excrement changes, in a long process, into grass and fruits.
A few examples of a najis thing changing into a tahir thing: A najis wood changes into ashes. The najis water changes into steam and becomes water again. The najis water which a cow drank changes into its urine or mills.
(Change in Properties)
Inqilab like istihalah means change. The difference is in the degree of change. In istihalah, the shape and form, all are changed; whereas in inqilab, only the properties change but the shape is not entirely changed. Its only example is of the wine changing into vinegar. When this change takes place, the vinegar becomes tahir.
(Change in Place)
Intiqal means change of place. Certain `ayn najis things can become ritually pure by change in its location or place. For example, human blood is najis. Now, if a mosquito sucks the blood of a man and the blood becomes `blood of mosquito', then it will become tahir. Similarly, if an organ of a kafir is transplanted to a Muslim (and after some time the organ becomes a part of the Muslim's body), then it will become tahir.
7. ZAWA LU `L-'AYNI 'N-NAJASAH
(Disappearance of the Najasat)
Zawalu ' 1- `ayni ' n-najasah means disappearance of the najis element. This mutahhir is mostly useful in case of animals.
If there is any najasat on the body of an animal, it will become tahir just by the removal of, or rubbing out, the najasat from its body.
Likewise, the inner parts of human body (like inside of the mouth, nose and eyelids) become tahir as soon as the najasat is removed from them. However, dentures are not included in this rule because they are foreign to mouth.
Istibra' means to clean something or to get rid of something.
This mutahhir is limited to certain animals. You already know that the urine and excrement of the halal animal are not najis. However, such animals loose their status of purity if they start eating human refuse. And when this happens, then the only way to make them tahir is istibra'.
Istibra', in this context, means keeping these animal away from eating human refuse for a specified number of days. The number of days depends on the type of the animal: the camel for 40 days, the cow for 20 days, the sheep or goat for 10 days, the duck or fowl for 5 or 7 days, and the chicken for 3 days.
Islam is the first among "the spiritual mutahhirat."
One of the a'yan najisah was a kafir. The only way a kafir can become tahir is for him/her to accept Islam. With the acceptance of Islam, he or she will immediately become tahir. However, if the person's clothes were najis, then the declaration of faith in Islam will not purify them; he will have to make them tahir with water.
Taba`iyyah means to follow. In the present context, it means that when a najis thing or person becomes tahir, the things which are related to them also become tahir automatically.
When a kafir becomes Muslim, his minor children become tahir automatically. If a well becomes najis, and the required amount of water is taken out of it to purify it, then the wall of the well, the bucket and the rope will also become tahir.
While washing a najis thing, our hands become najis also; but when that thing become tahir, our hands will also become tahir automatically. If the wine become vinegar, this change will make it tahir; and the pot which contained it, becomes tahir automatically .
The wooden plank or cement slab upon which the dead body of a Muslim is washed, as well as the piece of cloth used for covering his private parts, and also the hands of the person washing the dead body becomes clean when the ritual bath is completed.
11. GHAYBATU 'L-MUSLIM
(Disappearance of a Muslim)
The last among the mutahhirat is ghaybatu ' l-Muslim. I have counted it as one of the spiritual mutahhir because it is based on a most important moral teachings of Islam which says that one must be positive in judging other Muslims.
Ghaybatu 'l-Muslim means disappearance or absence of a Muslim. In the present context, it means the following: Suppose the body or anything related to a Muslim (who is serious in following the shari'ah) becomes najis.
Then that person goes out of your sight long enough for him to purify himself or his belongings. Now, he comes back and you see him using that particular thing, then you should consider it tahir.
E. OUR OUTLOOK
TOWARDS THE NAJASAT
What should be our general outlook towards the najasat? This is a question of utmost importance to the Muslims, especially for those who live in a society which is predominantly kafir. Usually we get two types of responses to this question: On the one hand is a group which has adopted a `liberal' view and says that such shari'ah laws are no longer relevant during our time. It is needless to say that this view has no support in the Islamic sources. The essence of Islam is a voluntary submission to the will of God and `liberal' attitude is opposite of that idea. The liberal view results partly from the ignorance about the dynamics and the adoptive nature of the shari'ah, it is the result of confusing the form for the substance; and partly from the influence of western liberal tradition. There is, on the other hand, a group which has adopted the holier-than-thou attitude and says that we must totally abstain from the najasat in all spheres of our lives. This view is based on some misconceived ideas about the shari'ah and the Islamic world-view in general. It ignores or is ignorant of the fact that Islam itself has described its shari'ah as "shari'atu 'n-sahla" or it shari`atu 'n-samha," a simple shari'ah, a lenient shari `ah.
While every informed Muslim recognizes the need to combat the liberal view, it is equally important to fight against the rigidity of the holier-than-thou mentality. The latter group is not without blame in pushing many ordinary Muslims towards the so-called liberal group. Between these two extremes lies the Islamic view, a view which can be named as the straight path-the path of those on whom Allah has showered His blessing, not of those with whom He is angry, nor of those who have gone astray! It is this view which I shall try, with the help of Allah subhanahu wa ta`ala, to explain here.
Let me begin by raising the following question: Should we start with the assumption that everything is najis and haram unless we come to know otherwise? OR Should we start with the assumption that everything is tahir and halal unless we come to know otherwise?
My answer to this question is that we should start with the assumption that everything is tahir and halal unless we come to know otherwise. Anyone familiar with the principles of the shari'ah cannot but agree with me. However, as all general rules have exceptions, the view I have adopted also has one exception. What I have said is valid at all times except in case of animal products obtained from non-Muslims. As for the animal products obtained from Muslims, we still start with the assumption that it is tahir and halal. It is only in case of the animal products obtained from the kuffar that we must start with the assumption that everything is najis and haram unless we come to know otherwise. This view is supported fully by all the mujtahids of our time, including Ayatullah al-Khu'i and Ayatullah al-Khumayni.
Here I wish to just quote Ayatullah Sayyid Muhammad Kazim at-Tabataba'i al-Yazdi a prominent Shi`a mujtahid of the early present century whose book al- `Urwatu' 1-wuthqa is used by later mujtahids as a text for their ijtihad lectures. Ayatullah al-Yazdi writes:
"(1) The utensils of the mushrikin and other kuff"ar are to be considered tahir as long as it is not known that they have touched them with flowing wetness. [This rule is valid] provided the utensils are not made from leather, otherwise they will be considered najis unless it is known that the animal [from which the leather originated] had been slaughtered Islamically or that it had been in possession of a Muslim [before coming into the kafir's possession].
"(2) Similarly other things that need to be slaughtered Islamically (e.g., meat and fat), if found in the possession of the kuff'ar must be considered najis unless it is known that the animal has been slaughtered Islamically or that it had been in possession of a Muslim [before coming to the kafir's possession].
"(3) However, a thing that does not need slaughtering is to be considered tahir unless you have knowledge that it is najis. And the conjecture that the kuff"ar may have touched it with wetness is not sufficient [to consider such a thing najis].
"(4) An item about which one is not sure whether or not it is from animal's .skin, flesh or fat is to be considered as a non-animal product and tahir, even if it is obtained from a kafir." 
All the mujtahids of our time have annotated the al-`Urwatu 'l-wuthqa and all of them have agreed with the above views of Ayatullah al-Yazdi. Although the above quotation is sufficient, but for the sake of clarity I would like to quote Ayatullah al-Khu'i. In the first volume of Minhaju 's-Salihiyn, under the section of najasat, he writes:
"What is obtained from the hands of the kdfirs -like bread, oil, honey and other similar things, whether they are liquid or solid- is tahir unless you come to know that they have touched it with flowing wetness. The same applies to their clothes and utensils. And conjecture about najasat [in such cases] should not be taken into account." 
But while discussing the rules of food and drinks, in the second volume of Minhaj, he writes:
"The skin, flesh and fat that is obtained from the hands of a kafir is to be considered najis even if he informs you that it has been slaughtered Islamically." 
What our mujtahids have said that you can assume everything --except the animal products obtained from a kafir- as tahir and halal unless you come to know otherwise is based on the clear guide-lines provided by our Imams (as).
Fuzayl bin Yasar, Zurarah bin A'yan and Muhammad bin Muslim, the three highly respected companions of the fifth and sixth Imams, asked Imam Muhammad al-Baqir (as) about buying meat from the markets while they do not know what the butchers do when slaughtering the animals. The Imam said, "Eat if it is from a Muslim market and do not question about it." 
Ahmad bin Muhammad bin Abi 'n-Nasr asked Imam 'Ali ar-Riza (as) about the [leather] shoes which have come in the [Muslim] market and a person buys a shoe while he does not know whether it [originated from an animal that] had been slaughtered Islamically or not. What do you say about praying in such a shoe while the person does not know [whether it is from a slaughtered animal]? Can he pray in it? The Imam said, "Yes; I also buy the shoes from the market, and it is made for me and I pray in it. You do not have to ask [whether it is from an Islamically slaughtered animal or not]."' 
al-Hasan ibn al-Jahm asked Imam 'Ali ar-Riza (as) a similar question about leather shoes and upon hearing the same answer, he said, "I am more restrained than this (in dealing with najasat)." Imam 'Ali ar-Riza (as) said, "Do you dislike what Abu '1-Hasan [i.e. Imam Musa al-Kazim] used to do?!" 
'Ali bin Abi Hamzah heard a person asking Imam Ja'far as-Sadiq (as) about a man who was praying while he was carrying a sword-can he pray with it? The Imam said, "Yes." Then the person asked, even if its sheathe was made of leather from an animal which might have or might not have been slaughtered Islamically? The Imam said, "If you know that it is from an un-Islamically slaughtered animal, then do not pray in it." 
An interesting incident is narrated by Mu'awiyah bin `Amman, one the famous companions of the sixth Imam. Mu'awiyah asked Imam Ja'far as-Sadiq (as) about the dress which is made by the Magi who are unclean, who drink intoxicants and their women are also of the same type: "Can I wear such a dress without washing it and pray in it?" The Imam said, "Yes." Thereafter, Mu'awiyah cut a shirt for the Imam from the cloth obtained from a Maji, designed it, and also prepared a waist-band and a robe from it. Then on a Friday, just before the noon time, he sent the dress to the Imam. He wanted to see whether or not the Imam puts it on without washing it. In Mu'awiyah's own words, "It seemed the Imam had understood my intentions, and came out with that same dress for the Friday prayer."  A somewhat similar question was put in writing to Imam Mahdi (as) about praying in a dress made by a Maji without washing. Imam Mahdi (as) replied, "There is no problem in praying in it." 
`Abdullah bin Sanari narrates that my father asked Imam Ja'far as-Sadiq (as), "I loaned my dress to a dhimmi kafir whom I know that he drinks intoxicants and eats pork, and then he returns it to me-do I have to wash that dress before praying in it?" The Imam said, "Pray in that dress and do not wash it for that particular reason because when you loaned it to him, it was tahir and now you are not sure about its becoming najis." 
The first four ahadith make it clear that whatever you get from a Muslim or a Muslim market -whether a non-animal product or an animal product- you can assume that it is tahir and halal, you do not even have to inquire about it. The last three ahadith make it quite clear that whatever non-animal products you get from a kafir is to be considered tahir and halal unless you come to know for sure that it is najis and haram.
The restrictions of a Muslim or Muslim market found in the first three ahadith clearly indicates that animal products can be assumed as tahir and halal provided they are from the Muslim market. It automatically follows that animal products from non-Muslim sources cannot be considered tahir and halal unless we come to know otherwise. Here I will just quote two more hadith on this specific issue:
Husayn bin al-Mundhir said to Imam Ja'far as-Sadiq (a. s.): We are a people who frequently go to the mountains and the distance is great between us and the mountains. We therefore buy animals in large number for food, and we ask the herdsmen about their religion and they reply that they are Christians. "So what do you say about the slaughtering of animals by the Jews and the Christians?" The Imam said, "O Husayn! The Islamic slaughtering can be done with Allah's name only and no one can be trusted with that except the people of tawhid (i.e., Muslims)." 
Once Ibn Abi Ya'fur and Mu'alla bin Khunays were travelling on the Nile and disagreed with each other about eating the meat slaughtered by the Jews. Mu'alla ate that meat while Ibn Abi Ya'fur refrained. Finally, they came to Imam Ja'far as-Sadiq (as) and informed him about their disagreement. The Imam approved the decision of Ibn Abi Ya'fur and disapproved Mu'alla's decision to eat that meat. 
I would like to end this section with an interesting comment by Ahmad bin Muhammad bin Abi 'n-Nasr al-Bizanti on the holier-than-thou attitude. Ahmad al Bizanti was a very trustworthy and educated companion of Imam Riza (as) and Imam Muhammad at-Taqi (as). Ahmad bin Muhammad bin `Isa asked Ahmad al-Bizanti about a person who buys a leather robe while he does not know whether it is from an animal that was slaughtered Islamically or not--can he pray in it? It is obvious that the question is about buying such a thing in a Muslim society. Ahmad al-Bizanti answered, "Yes, and you do not have to question about it. Imam Muhammad at-Taqi (as) used to say, `The Khawarij had put much restrictions upon themselves out of ignorance, whereas the religion is broader [in its outlook] than that."' The statement about the Khawarij has also been narrated from Imam Musa al-Kazim by Shaykh as-Saduq. 
It is on these shari'ah principles that our mujtahids have based their opinions about assuming everything -except the animal products obtained from a kafir to be tahir and halal unless we come to know otherwise. Islam does not expect us to totally abstain from najasat, it only wants us to be free from najasat in our food and drink, and during the salat.
. at-Tabataba'i, al-Mizan, vol. 9, p. 416; al-`Amili, Wasa'il vol. 1, pp. 249-51; al-Kadhimi, Masalik, p. 85.
. al-`Amili, Wasa'il, vol. 1, pp. 247, 1034.
. al-`Amili, Wasa'il, vol. 1, p. 1009.
. Masalik, p. 86; al-Ardibili, Zubdah, p. 31.
 Wasa'il, vol. 1, p. 1030.
. Wasa'il, vol. 1, p. 1050.
. Wasa'il, vol. 1, p. 1051.
. Wasa'il, vol. 1, p. 1055.
. Ibid, p. 1016.
 al-Jannati, Taharatu ' l-kitabi, p. 22-3; as-Sadr, al-Fatawa al-Wadiha, p. 221
. al-Yazdi, al-'Urwah, p. 24; al-Khumayni, Tahriru 'l Wasilah, vol. 1, p. 118.
 al-Gharawi, at-Tanqih fi Sharhi '1-`Urwati '1-Wuthqa (Lectures of Ayatullah al-Khu'i), vol. 2, p. 64; also see al Jannati, Taharatu ' l-Kitabi, p.27.
 al-Khu'i, Minhaju 's-Salihiyn, vol. 1 (Beirut, Daru 'z Zahra, 22nd ed.) p. 111.
. As quoted by Muhammad Jawad al-Mughniyya in Fiqhu '1-Imam Jafar as-Sadiq, vol. 1, p. 28.
. ar-Razi, Tafsir al-Kabir, vol. 27, p. 166.
. al-Yazdi, al-`Urwah, p. 52.
. al-Khu'i, Minhaj, vol. 1, p. 114.
. Ibid, vol. 2, p. 332.
. Wasa'il, vol. 16, p. 294.
. Wasa'il, vol. 1, p. 1072.
. Ibid, p. 1073.
. Ibid, p. 1072.
. Wasa'il, vol. 1, p. 1093.
. Ibid, p. 1095.
. Wasa'il, vol. 16, p. 279-80.
. Ibid, p. 285.
. Wasa'il, vol. 1, p. 1071