Menstruation is a natural process which takes place in woman's body every month. Before explaining the laws of the shari'ah about menstruation, it seems appropriate to discuss, in short, that why does this take place?
Allah has created the woman such that she plays the major role in the perpetuation of the human race. The primary reproductive organs of a woman are her ovaries. When a girl is born, her ovaries already contain about 400,000 immature eggs (which are known as ova). At puberty, the eggs start maturing, usually one ovum each month. The maturing of the ovum takes place roughly halfway between two menstrual cycles. After maturing, it finds its way from the ovary to the fallopian tube and ends up in the womb.
Meanwhile the womb (while preparing for the possible arrival of a fertilized egg) develops a thick, soft, velvety lining which is made up mostly of blood vessels.
This thick, soft lining in the womb is called endometrium.
If an egg is fertilized, it will be embedded in endometrium and continues its growth. But if no egg is fertilized, the endometrium (i.e. the lining of the womb) is no longer needed and is shed or discarded. This process of discarding the endometrium is known as menstruation.
From this biological explanation it is clear that menstruation is neither "the curse" on woman nor a result of the so‑called original sin of Eve. Rather it is a very normal biological process that ensures the perpetuation of the human race.
Of course, some women feel uncomfortable a few days before and during menstruation. This discomfort is caused by some of the biological changes which take place in the woman's body. Allah says, They ask you about menstruation. (O Muhammad), tell them that menstruation is a discomfort for the women, (it is a period when they pass through physical and emotional tension.) (2:222)
In this part of the book I intend, by putting my trust in Allah, to explain the Islamic laws (shari'ah) regarding the women who are in their monthly periods. First the definition of menstruation, its signs and its duration will be discussed; then comes the different categories of women who are in menstruation; followed by four chapters on the laws about the women in each category; and finally the acts which are forbidden to a woman during her periods and the manner of ghusl are explained.
2. DEFINITION OF HAYZ
There are four possible causes for discharge of blood from women:
2. Loss of virginity.
3. Post‑natal bleeding.
4. Internal injury.
As mentioned above, menstruation is different from the blood of group 2, 3, and 4. In the Islamic legal terminology, menstruation is known as hayz. And a woman who is having her period is known as haiz. 
According to Islamic laws, menstruation is the process of discarding the endometrium which normally takes place once a month in women from the day they attain puberty until they reach the age of menopause. (Menopause = final cessation of menstruation.)
From the shari'ah point of view, a girl attains puberty at the age of nine lunar years,  and she reaches menopause at the age of fifty. Imam Ja'far as‑Sddiq (upon whom be peace) said, "The age when a woman ceases to have menstruation is fifty years." 
So, if a girl sees blood before she becomes nine years old by lunar calendar, that blood is not considered menstruation (even if it may be regarded menstruation from the biological point of view). In the same way, if a woman sees blood after the age of fifty that blood will not be considered menstruation.
If a girl who does not know whether she has become nine years old sees blood on herself, then that blood cannot be considered menstruation even if it has all its three signs. (See below for the three signs of menstruation.) On the other hand, if a woman who doubts whether or not she has reached the age of menopause sees blood, then she should consider it as menstruation.
If a woman who has reached the age of menopause (i.e., fifty years) sees blood on herself with the three signs of menstruation or at the fixed time of her monthly periods, then what should she do? For such a woman, it is precautionarily wajib to act on precaution up to the age of sixty. Any blood seen after the age of sixty will be considered istihazah. (See part II for istihazah.)
"Acting on precaution" means to refrain from those things which are forbidden to a ha'iz and perform those things which are required of a woman in istihazah.
According to the shari'ah, it is possible for a pregnant woman and a nursing mother to have menstruation.
The Signs: If a woman is not sure about the nature of her discharge, then she should look for the following three signs of the menstrual blood: (a) warmth; (b) dark red or black colour; (c) pressure and slight burning in the discharge. If these three signs are found together, then it is menstruation.
These signs have been taken from a hadith of Imam Ja'far as‑Sddiq (peace be upon him). A woman came to him and asked, "What should a woman do who sees blood on herself but does not know whether it is menstruation or some other type (of blood)?" The Imam said, "The blood of menstruation is warm ...black (or dark‑coloured), and it has pressure and burning sensation..." The woman said, "By Allah! If he had been a woman, he could not have added anything further in this (description)!" 
3. DURATION OF HAYZ
The beginning of menstruation is determined when blood leaves the uterus and enters the vagina. It is necessary for the commencement of menstruation that the blood should be seen outside the vagina.
In another hadith, Imam as‑Sadiq said, "The minimum duration of menstruation is three days, and the maximum is ten days.” 
By "three days" we mean three days and the two nights between the first and the third day. For example, if blood starts on Monday morning and stops on Wednesday evening, then it is menstruation. And by "ten days" we mean ten days and the nine nights between the first and the tenth day.
So, if a woman sees blood for less than three days, it is not considered hayz. If the blood is seen for more than ten days, the ten days will be counted as menstruation and the blood seen after that will be regarded as istihazah.
The same Imam said, "The minimum duration of purity (between two menstrual cycles) must be (at least) ten days."  So if a woman sees blood during the ten days after her period had ended, it will not be considered hayz.
Although it is normal to say that menstruation takes place once "a month", but it should be clarified that menstrual cycles take place every 28 days ‑ so, in the present context "a month" means a period of 28 days, not 29, 30 or 31 days.
4. DIFFERENT CATEGORIES OF HA'IZ
According to the shari'ah, all the women are not same as far as the rules of menstruation are concerned. By taking into consideration the difference in regularity of time and days of monthly periods and their irregularity, women can be divided into three main groups:
1. Mubtadi'ah:literally, a beginner; in the present context it means a girl who sees menstruation for the first time.
2. Zatu 'l‑'adah:a woman who has menstruation regularly at a fixed time or for a fixed number of days or both. If a woman has two consequent periods with regularity in time of their occurance and duration, then she is a zatu 'l‑'adah = a woman who has formed a fixed pattern for her monthly periods.
On the other hand, if a zatu 'l‑'adah woman discovers that her fixed pattern for menstruation has changed and this happens for two consequent months, then she should follow the new pattern.
The zatu 'l‑'adah women can be of three types:
(a) a woman whose periods occur at a fixed time and for a fixed number of days. For example, on 1st of every month and lasts for 7 days continuously or with a pause on the fourth day.
(b) a woman whose periods occur at a fixed time but not for a fixed number of days. For example, on 1st of every month but sometimes for 4 days and at other times for 5 days.
(c) a woman whose periods occur for a fixed number of days but not at a fixed time. For example, she has her periods for 4 days but not at a fixed time, sometimes on 1st and sometimes on 4th of every month.
3. Muztaribah:a woman who does not have her periods with regularity. For example, a woman has her one period on the 1st of the month for five days and her second on the 5th of the month for three days and her third period on the 10th of the month for four days. Muztaribah here means a woman who has an irregular pattern for her monthly periods.
5. A GIRL ENTERING PUBERTY
The girl who reaches the age of puberty and sees her menstruation for the first time is known as mubtadi'ah = the beginner.
If a mubtadi'ah sees blood with the three signs for more than three and less than ten days, then it is menstruation.
But if a mubtadi'ah sees blood for more than ten days, then there are a few possibilites:
1. The blood was with the three signs for some days and without them for some other days, then the former is menstruation and the latter is istihazah.
2. The blood had the three signs during the entire flow but with a difference in intensity of colour, that is, some days it had black colour and some other days it had red or dark red colour. In this case the flow with black colour will be considered menstruation and the other will be considered istihazah.
3. If the entire flow was without the three signs or the flow with the three signs was less than three days, then the entire flow will be considered istihazah.
4. If the blood had the three signs during the entire flow, then the mubtadi'ah has to follow the numberpattern of the women in her family, e.g., her mother, sister, etc. That is, if her mother's monthly period comes for six days, then she should consider the six days as menstruation and the remaining days as istihazah.
But if the women in a beginner's family differ in the number‑pattern of their monthly periods, then during the first month she should observe six or seven days as menstruation and act on precaution up to the tenth day. In the subsequent months she should observe the first three days as menstruation and act on precaution up to sixth or seventh day. This alternate pattern should be continued until she forms a fixed pattern of her own.
If a girl loses her virginity and blood is discharged so much that she is uncertain whether the blood is from the loss of virginity or menstruation or both, then she should examine herself "by inserting a piece of cotton inside her vagina and leave it there for a while. Then she should take it out gently ‑ if the blood has just stained the outside of the cotton, then it is from the loss of virginity; but if the blood has penetrated into the cotton, then it is menstruation." 
If she is unable to examine herself, then she should consider herself whatever she was before losing virginity ‑ either she was pure from menstruation or not.
6. GENERAL RULES ABOUT ZATU 'L‑`ADAH WOMEN
The zatu 'I‑'adah women in groups (a) and (b) have to observe the rules of menstruation as soon as they see the blood. It makes no difference whether it starts on the fixed day, or one or two days before it or after it, even if it does not have all the three signs of menstrual flow. Of course, if she discovers that it was not menstruation (for example, the blood stopped on the second day), then she will have to perform her salat (which she had missed during the two days) as qaza.
The zatu 'l-adah women in group (c) have to observe the rules of menstruation if the blood has all the three signs of menstrual flow mentioned above. If the discharge does not have all the three signs, then it will not be regarded as menstruation.
When a zatu 'l‑'adah woman sees blood many days before or after the fixed time then if it has the three signs altogether, it is menstruation; otherwise it will be regarded as istihazah.
with 3 signs = hayz.
without 3 signs = istihazah.
with 3 signs = hayz.
without 3 signs = istihazah.
But as mentioned above, if a zatu 'I‑'adah woman sees blood during the fixed time, it is hayz even if it does not have the three signs.
with or without 3 signs = hayz.
If a zatu 'I‑'adah woman sees blood for three days and then it stops for some days and again it comes for three more days ‑ then both flows of blood and the pause between them will be considered hayz only if (a) the total days of two flows and the pause between them is not more than ten, and (b) all these days are in the fixed time and fixed number of days of the woman's menses.
if total of 2 flows & the pause is ten or less + all these days are in
the fixed time = hayz.
In the following three cases also, the two flows of blood and the pause between them will be counted as hayz:
i. If one of the flows started a day or two before the fixed time.
both flows and the pause = hayz.
ii. If both flows started outside the fixed time but both had the three signs of menstrual flow.
with 3 signs ‑ hayz.
without 3 signs = istihazah.
iii. If one flow (which started outside the fixed time) had the three signs while the other flow started in the fixed time.
with 3 signs = hayz.
without 3 signs = istihazah.
But if one flow or both did not have the three signs of menstruation and none of them occured in the fixed time, then the flow with the three signs is menstruation and without them is istihazah.
If the total days of both flows is more than ten and the pause between them is less than ten days, then the following procedure is to be followed:
i. If one of the flows was in the fixed time without the other, the one within the fixed time will be considered hayz and the other one istihazah.
ii. In the case where none of the flows occurred in the fixed time, then
(a) if one had the three signs but not the other ‑ the one with the signs will be hayz and the other istihazah.
(b) if both flows had the three signs, then the first will be considered hayz and the other will be considered istihazah.
If the pause between the two flows of blood was ten days or more, then in the following two cases they will be considered two separate menstruations:
i. if both flows had the three signs:
with 3 signs = two separate hayz.
without 3 signs = two separate istihazah.
ii. if one was in the fixed time, while the other had the three signs.
If these blood flows occured outside the fixed time and without the three signs, then both will be counted as istihazah.
If the blood stops before ten days and the woman is uncertain whether or not it has stopped completely, then she should examine herself by inserting a piece of cotton inside her vagina and leave it there for a while. Then she should take it out gently ‑ if the cotton comes out dry, she should consider herself pure and perform ghuslu 'I‑hayz (unless the pause during menstrual flow is normal in her case).
While examining oneself, it is better "to stand upright leaning on a wall, etc, and lift up one leg and then insert the cotton into the vagina." 
If such a woman (who is uncertain whether or not her period has stopped completely) does not examine herself and performs ghuslu 'I‑hayz, then her ghusl is valid only if the menstrual flow does not start again.
And if she is unable to examine herself, then she should consider herself ha'iz until she is sure of her purity.
But if the cotton comes out stained with blood, the rules differ slightly for the different categories of ha'iz:
If a mubtadi'ah, a muztaribah and a zatu 'l-adah who has her periods for 10 days examine themselves and find that the cotton is stained, then they should consider themselves as ha’iz up to ten days or until the blood stops.
If a woman who has her periods regularly for less than ten days examines herself during her fixed numbers of days and finds the cotton stained, then she should consider herself ha'iz. If the same woman examines herself outside her fixed numbers of days and finds the cotton stained, she should consider herself as ha'iz for up to ten days or until she finds herself pure.
If a zatu 'l‑'adah woman of group (c) sees blood for more than ten days, then she should consider her fixed number of days as menstruation (even if it is without the three signs); and the remaining days should be considered as istihazah(even if it is with the three signs).
But if both flows can be counted as one hayz, then she should do so. For example, she saw her first flow according to her pattern for three days, then blood stopped for four days and started again (with the three signs) for three days (making a total of ten days) and then continued (without the three signs) afterwards ‑ then she would count the first flow + intervening pause + second flow of three days (with the signs) as hayz and the remaining period as istihazah.
first flow + pause + second flow with 3 signs = 1 hayz.
later part of 2nd flow without 3 signs = istihazah.
7. THE FORGETFUL ZATU 'L‑'ADAH WOMEN
1. If a woman who has her periods on fixed number of days but not on fixed time (group c) forgets the duration of her menses, then she has to act as follows:
She has the menstrual flow for three or more days, then all those days will be considered as hayz if they are not more than ten.
But if they are more than ten, then the number of days which she considers as the probable duration of her menses should be counted as hayz and the remaining days will be counted as istihazah. And if the "probable duration of her menses" is more than seven days, then she should act on precaution from the last probable day up to the tenth day.
2. A woman who has a fixed time for the occurance of her periods (group b) forgets that fixed time:
If she has the menstrual flow for three or more days, then all those days will be considered as hayz if they are not more than ten.
In the case the days are more than ten, and if she knows on the whole that the bleeding has coincided with her fixed time ‑ then she should act on precaution for the whole period of the flow even if the blood does not have the three signs of menses.
But if she does not know even generally that the bleeding has coincided with her fixed time, then there are two possibilities:
i. The blood flow had the three signs for some days and did not have the three signs for some other days ‑ then the days with the three signs will be considered as hayz if they are not more than ten, and the other days will be considered as istihazah.
ii. The blood had the three signs during the entire flow or for more than ten days, then six or seven days should be considered as hayz and the remaining as istihazah. In this case it is precautionarily better for her to act on precaution up to the tenth day.
3. A woman who has a fixed time for the occurance of her periods and a fixed number of days for its duration (group a) forgets her fixed time or fixed number of days or both, then there are a few possibilities:
(a) She forgot the fixed time but remembers the fixed number of days: If she has the menstrual flow for three or more days, then all those days will be considered hayz if they are not more than ten.
In case the bleeding continues for more than ten, and she knows on the whole that the bleeding has coincided with the fixed time ‑ then she should act on precaution for the whole period of the flow even if the blood does not have the three signs of menses.
But if she does not know even generally that the bleeding has coincided with the fixed time, then she should consider the fixed number of days (which she remembers) as menstruation and the remaining days as istihazah.
(b) She forgot her fixed number of days but remembers the fixed time of occurance: The blood she sees at the fixed time ‑with or without the three signswill be considered menstruation if it is not for more than ten days. If it comes for more than ten days, then she should consider the probable number of days from the fixed time as menstruation and the remaining days as istihazah. And in this case if the probable number of days is more than seven, then she should act on precaution up to the tenth day.
(c) She forgot both the fixed time and the fixed number of days of her monthly periods:
i. if the blood has three signs and it came for not less than three and not more than ten days, then all of it will be regarded as hayz. If it exceeds ten days, then the days she considers as the probable days of her monthly period will be considered as hayz and the remaining days as istihazah. Again in this case if the probable period is more than seven, then it is better for her to act on precaution up to the tenth day.
ii. if the blood is with the three signs for some days but without them for some other days ‑the former will be menstruation and the latter istihazah. Of course, if both these flows are not more than ten days, then it is better for her to act on precaution on the days when the blood is without the three signs.
iii. If the blood comes for ten days or more than ten days and the woman knows on the whole that the bleeding has coincided with her fixed time and number of days, then she should act on precaution for the entire period ‑ even if the blood did not have the three signs.
8. THE MUZTARIBAH
If a muztaribah sees blood with the three signs for more than three and less than ten days, then it is menstruation.
But if a muztaribah sees blood for more than ten days, then there are a few possibilites:
1. The blood had the three signs during the entire flow, then she should consider six or seven days as menstruation and the remaining days as istihazah.
2. The blood had the three signs during the entire flow but with a difference in intensity of colour, that is, some days it had black colour and some other days it had dark red colour. In this case the flow with black colour will be considered menstruation and the other will be considered istihazah ‑ if such dark colour was not less than three and not more than ten days.
3. The blood was with the three signs for some days (but not less than three and not more than ten days) and without the signs for some other days, then the flow with the three signs is menstruation and without them is istihazah.
4. If the entire flow was without the three signs or the flow with the three signs was less than three days, then the entire flow will be considered istihazah.
9. THE THINGS FORBIDDEN TO THE HA'IZ
I have already mentioned that menstruation is neither a "curse on the women" nor is it related to the so‑called original sin of Eve.
Menstruation is the flow of blood; and blood, according to the shari'ah, is a najis (unclean) substance and so menstruation is also considered najis. But the impurity of menstruation in no way prevents a woman from living a normal life with her family and friends.
A person asked Imam ja'far as‑Sadiq (peace be upon him) about a woman who gives water to a man while she is in her monthly period. The Imam said, "One of the wives of the Prophet (upon whom be peace) was pouring water on him and serving him drink while she was in her monthly period." In another tradition, Imam Muhammad al‑Baqir (peace be upon him) narrates that the Prophet (upon whom be peace) said to one of his wives, "Serve me a drink." She said, "I am in my monthly period." The Prophet said, "Is your menstruation in your hand?!"  These two narrations are sufficient to show that the impurity of menstruation does not prevent a woman from living a normal life with her family and friends.
On the other hand, there are certain acts of worship, etc., in Islam which are so sacred that a Muslim, whether man or woman, cannot perform them unless he or she has certain qualifications. It is only in relation to these acts that the women who are in menstruation, just as the junub men, are forbidden from performing them. Those acts are as follows:
1. Touching the writings of the Qur'an, the names and attributes of Allah, the names of the Prophet, the Imams and Fatimah (the daughter of the Prophet). It is better not to touch names of other prophets too.
2. Reciting those verses of the Qur'an in which sajdah (prostration) is wajib, i.e., verse 15 of chapter 32; verse 37 of chapter 41; verse 62 of chapter 53; and verse 19 of chapter 96. It is better not to recite even a single verse from these chapters.
3. Staying or even entering in a mosque. One can pass through the mosques  (by entering from one door and leaving from the other) except the Masjidu l‑Haram (the Sacred Mosque at Mecca), Masjidu 'n‑Nabi (the Mosque of the Prophet at Medina), and the shrines of the Imams ‑ a ha'iz woman cannot even pass through these places.
As she is not allowed to enter any mosque, naturally she cannot do circumambulation (tawaf) of Ka'bah, nor can she observe i'tikaf. 
4. Putting something in a mosque ‑ even if she is standing outside. But she may take out something from it ‑ provided she does not enter it.
5. A woman who is in her periods is excused from salat (prayers) because she does not have an important qualification for salat, i.e., taharat (cleanliness). She does not even have to perform them later on as qaza. Imam 'Ali Raza (peace be upon him) said, "When a woman has her monthly period, she does not ...pray because she is in the state of impurity (of blood), and Allah likes to be worshipped only by a pure (tahir) person..." 
6. Likewise a ha'iz woman is excused from fasting; but in this case, she has to fast after the month of Ramadhdn as qaza. In his answer to Abu Basir's question, Imam Ja'far as‑Sadiq said, "Fasting is just for a month in a year while salat is every day and night. That is why Allah ordered that the fasts (missed by a ha'iz in Ramadan) be repaid as qaza, while He did not order to perform qaza of the salats (missed during hayz). " 
It is mustahab for a ha’iz to change her sanitary napkin at the time of every prayer, to do wudu', to sit on her musalla facing the qiblah and to recite du'as; it is better to recite tasbihat arba'ah. (Tasbihat arba'ah are as follows: subhan Allahi; wa 'I‑hamdu li 'I‑lahi; wa la ilaha illa 'lahu; wa 'la‑lahu akbar.)
It is makruh for a ha’iz to recite, to keep, to carry or to touch the border of the pages of the Qur'an, or the blank space between the lines.
At the end of this chapter I would like to present the following verses from the Bible so that the reader may appreciate the laws of the shari'ah. The Bible, in the Book of Leviticus, says,
"When a woman has a discharge, her discharge being blood from her body, she shall remain in her impurity for seven days; whoever touches her shall be unclean until evening. Anything that she lies on during her impurity shall be unclean; and anything that she sits on shall be unclean. Anyone who touches her bedding shall wash his clothes, bathe in water, and remain unclean until evening; and anyone who touches any object on which she has sat shall wash his clothes, bathe in water, and remain unclean until evening. Be it the bedding or be it the object on which she has sat, on touching it he shall be unclean until evening. And if a man lies with her, her impurity is communicated to him; he shall be unclean seven days, and any bedding on which he lies shall become unclean.
"When she becomes clean of her discharge, she shall count off seven days, and after that she shall be clean. On the eighth day she shall take two turtledoves or two pigeons, and bring them to the priest at the entrance of the Tent of Meeting. The priest shall offer the one as a sin offering and the other as a burnt offering; and the priest shall make expiation on her behalf, for her unclean discharge, before the Lord." (Lev. 15:19‑30)
Now surely you will appreciate the words of Allah which say, Allah does not desire to make any impediment for you; He only desires to purify you, and that He may complete His blessings upon you; haply you will be thankful (to Him). (Qur'an 5:6)
10. SEX DURING MENSTRUATION
By considering the discomfort of the women during the monthly periods, Islam has forbidden both the husband and the wife from sexual intercourse during the menstruation.
The Qur'an says, They ask you about menstruation. (O Muhammad) tell (them that) menstruation is a discomfort (for the women, it is a period when they pass through physical and emotional tension. Therefore,) do not establish sexual relations with them during the menses, and (again you are reminded that) do not approach them (sexually) until the blood stops. Then when they have cleansed themselves, you (are permitted to) go into them as Allah has commanded you (by placing sexual urge in your nature). (2:222)
Of course, playing with the other parts of her body (other than the vagina and anus) is allowed. Again, it is precautionarily better not to play with her body between the navel and knees.
If a man who is engaged in sexual intercourse with his wife discovers that her period has began, then he should immediately withdraw himself from her.
It is clear from the verse mentioned above (until the blood stops) that once the blood has stopped, intercourse becomes lawful even if the woman has not performed ghuslu 'l‑hayz. But on the basis of the subsequent sentence (then when they have cleansed themselves...), most of the fuqaha' (Islamic jurists) have ruled that it is precautionarily better to refrain from intercourse until she performs ghusl or, at least, washes her private parts.
'Ali bin Yaqtin asked Imam Musa al‑Kazim (peace be upon him) about a man having intercourse with his wife whose period has stopped but she has still not performed the ghusl. The Imam said, "There is no harm in it; but (intercourse) after the ghusl is more preferable to me.` 
11. THE SALAT BEFORE & AFTER THE MENSES
Whenever a mubtadi'ah, a muztaribah or a forgetful zatu 'l‑'adah woman sees blood, she should stop her salat ‑ of course, if she discovers later on that it was not hayz (e.g., the blood stopped on the second day), then she should perform qaza of the salat which she had missed.
If the time for a particular salat has already begun and a woman fears that by delaying the salat her period may start, then it is wajib on her to perform that salat immediately.
If the time for a particular salat has already begun and the woman did not pray until her period started, then she has to perform that salat as qaza after the menstruation stops and she becomes clean.
If a woman's period starts while she is engaged in salat, her prayer will be invalid.
If a woman who is engaged in salat doubts whether or not her period has started, her doubt will have no effect on the salat unless she discovers later on that her period had actually begun.
If a woman becomes pure from menstruation and has enough time to perform ghuslu 'I‑hayz and pray, at least, one rak'at in time ‑ then it is wajib on her to do so. In case she does not pray, then it will be wdjib on her to perform its qaza.
For example, the time of 'asr prayer was ending at 5:00 p.m. and a woman became pure from her period at 4:00 p.m. In this case, she has enough time to perform ghuslu 'l‑hayz and pray salat of 'asr. If she does not do so, then it will be wajib for her to perform salat of `asr as qaza.
If a woman becomes pure from menstruation while she does not have enough time to perform ghusl and pray at least one rak'at in time ‑ then it is precautionarily obligatory for her to perform tayammum instead of ghusl, and pray. But in this case if she does not do so, then it is not wajib for her to perform that salat as qaza.
12. GHUSL U'L‑HAYZ
When a woman becomes pure from menstruation, it is wdjib for her to perform ghusl. Apart from sexual intercourse, all the acts forbidden to her will remain so until she performs ghusl u'I‑hayz.
The manner of performing ghuslu 'l‑hayz is same as the method explained in Wudu' & Ghusl. For convenience of the reader, the manner of performing ghusl is also given here.
There are two methods of performing ghusl: Ghusl tartibi and ghusl irtimasi.
1. Ghusl Tartibi: After removing the najasat from the body and after niyyat, the body has to be washed in three stages: First, the head and the neck; then the right side of the body from the shoulders to the foot; and lastly, the left side of the body.
2. Ghusl Irtimasi: In this type of ghusl, after niyyat, the whole body should be completely immersed in water at once, not gradually. One has to make sure that all the parts of his body, including the skin under the hair, has been washed.
However, ghusl tartibi is preferred to ghusl irtimasi.
For other details about the manner of performing ghusl, see pp. 16‑20of Wudu' & Ghusl.
 To make the pronounciation easier for the readers, I have departed from the standard transliteration method of writing as d; instead I have used z. For example, instead of haid and hayd, I have written ha'iz and hayz respectively.
 Nine years according to the Islamic (lunar) calendar would be eight years and nine months according to the Gregorian (solar) calendar.
 al‑'Amili, Shaykh Muhammad bin Hasan al‑Hurr, Wasa'ilu 'sh‑Shi'ah, (kitabu 't‑Taharah), (ed. 'Abdu 'r‑Ralum ash‑ShirdA) vol. 2, Tehran 1401 AH, p. 580.
 Ibid, p. 537.
 Ibid, p. 551.
 Ibid, p. 554.
 As explained by Imam Musa al‑Kazim (peace be upon him) to Khalaf bin Hammad al‑Kufi. See al‑'Amili, op. cit., vol. 2, p. 535.
 As explained by imam as‑Sadiq. See al‑'Amili, op. cit., vol. 2, p. 562.
 al‑'Amili, op. cit., vol. 2, p. 595.
 It is necessary to clarify that mosque, i.e., masjid, is different from the religious centres built by the Shi'ahs in the memory of Imam Husayn (peace be upon him) which are usually known as Husayniyyah, Imambargah or Imambara.
 I'tikaf means to fast and stay in a mosque for at least three days with the intention of worshipping Allah.
 Ibid, p. 586.
 Ibid, p. 591.
 Ibid, p. 573.