He who disbelieves in Allah after his belief in Him, (is the liar) except he who is compelled while his heart remains steadfast with the faith (has nothing worry). But who opens his breast for infidelity; on these is wrath of Allah, and for them is a great torment. 
This verse of the Qur’an refers to the incident when 'Ammar bin Yasir (May Allah be pleased with both) had to utter some words against Islam to save himself from the Quraishite infidels.
It clearly allows hiding one 's true faith when one is in danger of one's life. This rule is called taqiyah.
Question 1: What is the meaning of "Taqiyah"?
Answer: Its literal meaning is to safeguard; to defend; to fear; piety (because it saves one from the displeasure of Allah).
This gist of above is that the word taqiyahmeans to be on guard, to fear, to be pious.
The dictionary as‑Surah says, (Taqiyah, tuqat = piety)
Question 2: What is its significance in Islamic terminology?
Answer: In Islamic terminology it means "to save life, honour. or property (either one's own or of other believers) by hiding one's belief or religion". 
Question 3: Is it something peculiar to the Shi'ism, because I have heard many people accusing the Shi'as because of taq'iyah?
Answer: Every society, religion and group practices it and has practiced it at one time or the other. You will find so many examples of taqiyahin the Old and the New Testaments, and even in the lives of the Holy Prophet of Islam, his Companions and many Sunni scholars.
Question 4: But is this practice allowed in Islam?
Answer. Yes. Allah has allowed it in the Qur’an; and reason too shows the wisdom of this permission.
Shah `Abdul `Aziz Dehlawi writes: "It should be known that taqiyah is, in fact, allowed by shari`ah, by authority of the Qur’anic verses, "except when ;you have to guard against them" ; and "except he who is compelled while his heart remains steadfast with the faith.” 
Famous Sunni scholar, `Allamah Wahidu 'z‑zaman Khan of Haydarabad (India) says: "Taqiyah is proved from the Qur’an, "except when you have to guard against them"; and ignorant people think that taqiyah is something peculiar to the Shi'as, while it is allowed in the Sunni faith also at times." 
Question 5: If you hide your belief and declare yourself to believe in some anti‑Islamic tenets, won't you automatically go outside the pale of Islam and become a 'Kafir'?
Answer: Belief and faith as well as the disbelief or rejection of faith (in short, Iman and Kufr) are basically the matters of "heart". That is why Allah rebuked those newly‑converted Arabs who claimed to be `Believers':
The desert Arabs‑say: "We believe" : Say (unto them): "You believed not; rather say "we accepted Islam" be cause the Faith has not yet entered your hearts ". 
The declaration by tongue has a very minor role in it., A belief without declaration is acceptable but a declaration without belief is condemned in the Qur’an in severest terms:
When come unto thee the hypocrites, they say: "We bear witness that verily you are the Messenger of Allah"; and verily Allah knows that you are certainly this Messenger; and verily Allah bears witness that the hypocrites are certainly the liars. 
Now remember that the life of a Muslim is very precious in the eyes of Islam. The importance attached to even one life is seen in this verse:‑
And he who saves it (i.e., a human life) shall be as though he has saved the whole mankind. 
And a Muslim is bound to save a life from unlawful destruction, whether it is some one else's or his own:
And cast not yourselves with your own hands into perdition. 
It is for this reason that suicide has been declared a capital sin just like murder; and it is for this reason that Shi'a Shari`ah does not allow starting a jihad (war) without permission of the Prophet, Imam or their especially appointed deputies or in defense.
And it is to save the life of a believer that one is allowed to utter a lie and save that precious life.
Question 6: All Right. You saved a life; but you committed one of the greatest sins, i.e., lie. So, spiritually you are doomed to disgrace in either case. Then, why not tell the truth and let the enemies kill you if they want?
Answer: When a person is in such a situation that no matter whichever course of action he chooses he has to commit an evil, then the reason says that he should select the lesser evil.
Or if he is forced to destroy or damage one of his two possessions, then surely he would damage or destroy the less‑expensive item to save the more precious one.
Imam Fakhru 'd‑din ar‑Razi says commenting on the events of the Prophet Musa (as) and Khidr (as), mentioned in Surah al‑Kahf:
When one is confronted by two damaging alternatives, it is wajib to bear the lesser one in order to ward off the greater one; and this was the principle followed in the three actions (done byKhidr)’. 
Islamic Shari`ah abounds with examples of this principle. Prayer is the most important pillar of Islam. But if you are praying and a child falls down a well, and there is no one else to save the child, the Shari’ah commands you to leave your prayer, and try to save the child. If you ignored this command, that prayer would not be accepted, and you would be guilty of neglecting to save a life.
Now, suppose the unbelievers are determined to kill a Muslim, not because he has committed any crime but just because of his faith. The said Muslim goes into hiding and you know where he is. The unbelievers come to you and ask you whether you knew where that person was. You are caught between two evils: either you say `No' and become a liar, or you say `Yes' and cause the murder of an innocent Muslim. The reason says that telling a lie in that situation is preferable than the truth which would lead to murder. 
Now suppose that the unbelievers have caught a Muslim and that Muslim happens to be `You'. They put two alternatives before you: Either renounce Islam or be killed. If the flame of true Faith is lighting your heart, mere words of tongue cannot extinguish it at all. Those words of disbelief will be just like a dark cover to hide the light of your faith from the unbelievers, but they can have no adverse effect on the flame itself.
And if you do not hide that flame behind that cover, your life will be forfeited and with that you will lose the possibility of serving Islam at some other time.
In short, by uttering a few false words against Islam you will save your life as well as your faith; and by not uttering those words your life will come to its end and with it will vanish all chances of Islamic services which you could have rendered had you been alive. Allah, therefore, has allowed you to save your life by uttering a few false words against Islam. 
Question 7: Say whatever you like, but the fact remains that taqiyah is just another form of Nifaq (hypocrisy).
Answer. Far from it. In fact taqiyah is opposite of Nifaq. Remember, Iman and Kufr, when seen with their `declaration', can be divided in four categories only:
(1) Correct belief of Islam by heart and its declaration in words.
This is open Iman (faith).
(2) Belief against Islam by heart and expression of that anti‑Islamic belief in words.
This is open Kufr (infidelity). These two categories are opposite to each other and cannot combine in one place.
(3) Belief against Islam in heart but declaration of Islam in words.
This is Nifaq (hypocricy).
(4) Correct belief of Islam by heart but declaration of anti‑Islamic belief in words.
This is taqiyah, and these two categories (Nifaq and Taqyah are, likewise, opposite to each other and can never be found in one place. 
Question 8: You claimed above that many companions of the Holy Prophet practiced it. Can you give an example?
Answer. We have mentioned in the very beginning the example of 'Ammar bin Yasir (ra): The Quraishites brutally martyred Yasir and his wife Sumaiyah just because of their faith. They were the first martyrs of Islam. When the parents were killed, 'Ammar pretended to renounce Islam, and thus saved his life. Someone told the Prophet that 'Ammar had become kafir. The Prophet said: "Never; verily the flesh and blood of 'Ammar is saturated with true faith." Then 'Ammar came to the Holy Prophet bitterly weeping that he had to utter evil words against Islam so that he could slip away from the clutches of the infidels. The Prophet asked him; `How did you find your heart?" 'Ammar said: "Steadfast in Faith". The Holy Prophet told him not to worry and advised him to repeat those words if the infidels again asked him to do so.
And it was not only the Holy Prophet who liked the choice of 'Ammar (ra). Even Allah confirmed his action in the verse which has been written in the beginning:
He who disbelieves in Allah after his belief in Him (is the liar) except he who is compelled while hiS heart remains steadfast with the faith (has nothing to worry). But he who opens his breast for infidelity, on these is the wrath of Allah, and for them is a great torment. 
All commentaries of the Qur’an narrate that it was revealed concerning the above incident of 'Ammar (ra). 
Question 9: Is there any other verse sanctioning such a cause of action?
Answer: Yes. See the following verse which says:
Let not the believers take the disbelievers as their friends rather than the believers; whoso shall do this then he has no relation with Allah except when you have to guard Yourselves against them for fear from them; but Allah cautions you of Himself for unto Allah is the end of your journey. Say, whether you conceal what is in your hearts or manifest it, Allah knows it; and He knows all that is in the heavens and all that is‑in the earth; and verily Allah has power over all things. 
The reason of this permission is given in this very aya: "Say whether you conceal what is in your hearts or manifest it, Allah knows it". Here Allah assures the Muslims that Faith is a spiritual thing, connected with heart;. and if your faith inside your heart is un‑impaired, then Allah is pleased with you whether you manifest that faith or hide it. It is all the same with Allah, because He knows your hidden secrets, and even when you hide your faith from unbelievers, Allah knows it and recognizes it.
As explained in reply to Question No. 1, taqiyah and tuqat both are synoynmous.
as‑Suyuti writes inter alia under this verse:
"And Ibn Jarir and Ibn Abi Hatim have narrated through al‑`Awfi from Ibn 'Abbas (that he said about this verse): `So taqiyah is by tongue. Whoever is compelled to say something which is disobedience of Allah and he speaks it because of those people's fear while his heart remains steadfast in the faith, it will do him no harm; verily taqiyah is with the tongue only.'
"…. And `Abd ibn Hamid has narrated from al‑Hasan (al‑Basri) that he said: `Taqiyah is lawful upto the day of resurrection. And `Abd (ibn Hamid) has narrated from Abu Raja' that he was reciting, `illa an tattaqu minhum taqiyatan'; and `Abd ibn Hamid has narrated from Qatadah that he was reciting (likewise) .... taqiyatan with ya”. 
Imam Fakhruddin ar‑Razi has mentioned some rules concerning taqiyah under this verse, some of which are given here:
"Third Rule: Taqiyah is allowed in matters related to manifestation of friendship or enmity; and it is also allowed in matters connected to professing (their) religion. But it is certainly not allowed in matters which affect other persons, like murder, fornication, usurpation of property, perjury, slander of married women or informing the unbelievers about the weak points in the Muslims' defence.
"Fourth Rule: The Qur’anic verse apparently shows that taqiyah is allowed with dominant unbelievers. But according to the madhhab of Imam Shafi'i (May Allah be pleased with him) if the condition between (various sects of) the Muslims resembles the condition between the Muslims and the polytheists, then taqiyah (from the Muslims too) is allowed for the protection of one's life.
"Fifth Rule: Taqiyah is allowed for protection of life. The question is whether it is allowed for the protection of property; possibly that too may be allowed, because the Prophet (saw) has said: `The sanctity of a‑Muslim's property is like the sanctity of his blood'; and also he (saw) has said: `Whoever is killed in defence of his property, is a martyr'; and also because man greatly needs his property; if water is sold at exorbitant price, wudhu' does not remain wajib and one may pray with tayammum to avoid that small loss of property; so why should not this principle be applied here? And Allah knows better.
"Sixth Rule: Mujahid has said that this rule (of taqiyah) was valid in the beginning of Islam, because of the weakness of the believers; but now that the Islamic government has got power and strength, it is not valid. But `Awfi has narrated from al‑Hasan (al‑Basri) that he said: `Taqiyah is allowed to the Muslims upto the day of resurrection.' And this opinion is more acceptable because it is wajib to keep off all types of harm from one's self as much as possible."
Imam Bukhari has written a full chapter, Kitabul Ikrah, on this subject of compulsion, wherein he writes, inter alia:
And Allah said `except when you hale to guard yourselves against them for fear from them’. And it is Taqiyah.
.... And Hassan (Basri) said: `Taqiyah is upto the Day of Resurrection .... And the Prophet (s.a:w.) said: `Deed are according to intention. 
As‑Sayid ar‑Radi (the compiler of Nahj ul Balaghah) writes, inter alia, in explanation of the verse 3:28‑29:
"Then Allah made an exception (in. this rule of not keeping friendship with the unbelievers) and that exception is the situation of taqiyah; so he said
and it is also read (taqiyatan), and both words have the same meaning.
"It means that Allah bas permitted in this situation (when one is afraid of ahem) to show their friendship and one's inclination towards them `with tongue' but not with intention of heart." 
Also, there are four verses in the Qur’an which allow eating unlawful food when one is starving to death and no lawful food is available: One of them says:
Verily, verily; He has but prohibited that which dies of itself and blood and swine flesh and whatsoever has other name than Allah's invoked upon it; but whoever is forced to it without the desire (for it) not to transgress (the limits) then it a no sin on him; verily Allah is Forgiving, Merciful'. 
The same thing has been repeated in 5:3, 6:145 and 14:115.
As explained earlier, the life of a believer is the most precious thing. And it is for this reason that one has been allowed to eat such abominable things as dead body or pork when life depends on it.
The same principle will apply if safety of life depends on uttering a few false words.
That is why the Prophet (saw) has categorically said:
He who has no taqiyah has no religion. 
And Imam Muhammad al‑Baqir (as) has said:
Taqiyah is religion and the religion of my forefathers: He who has no taqiyah has no faith. 
Question 10: Though this practice is allowed in the Qur’an and hadith, nevertheless it is something evil. I do not believe that Allah would like us to resort to it even if it is allowed.
Answer. You have just now seen that taqiyah is not only allowed but even wajib in some cases. Do you think that Allah would make something wajib without liking it. Also, the Prophet (saw) makes taqiyah synonymous with religion, and Imam Muhammad al‑Baqir (as) confirms it in clear words.
However, if you ponder on the Qur'an you will see that the Holy Book of Allah presents taqiyah in a very commendable light. In the verse 40:28 Allah says:
And said a man who was a believer from among the people of Pharaoh: who used to conceal his faith … 
It shows that Allah was well‑pleased with that hiding of the faith because it had great benefits, as Abu Talib kept his faith secret because it had great benefits. Just because Abu Talib did not announce his Faith, he was able to protect the life of the Holy Prophet (saw): Likewise, that believer from the family of Pharaoh was able to protect Prophet Musa (as) by not declaring his Faith openly.
Anyhow, his Faith based on taqiyah was so pleasing to Allah that he was counted as a "Siddiq" (Most Truthful). The Holy Prophet (saw) has said:
"There are three siddiqin: (1) Habib Najjar; (2) The faithful from the family of Pharaoh arid (3) 'Ali bin Abi Talib". 
Not only "the Believer from the Family of Pharaoh" but, according to Al‑Baidawi, even the Prophet Musa (as) had spent a considerable period of his life in taqiyah: See his Commentary under the following ayat,
Said (Pharaoh): Did we not cherish you amidst us as a child? And you did dwell amidst us for years of your' life. 
Coming back to the time of the Holy Prophet of Islam, we know that the Holy Prophet kept his Mission secret for 3 years; and we have seen how 'Ammar bin Yasir resorted to taqiyah. This was in Meccan period. Even after Hijrah there remained in Mecca many believers whose Islam was unknown to others. When the peace of treaty was concluded in Hudaibiyah in 6 A.H. many Muslims were displeased with its terms.
Hadhrat Umar bin Khattab was so incensed that he protested to the Holy Prophet (saw), and in later days he used to say:
I did not entertain any doubt about the prophethood of the Holy Prophet‑since I accepted Islam exc;pt on that day of Hudaibiyah. 
Replying to that group, Allah explains one of the reasons of that treaty and one of the causes why war was not waged at that time:
And were it not for the believing men ‑ and believing women, not having known them you might' have trodden them down; a crime would have afflicted you because of them without (your) knowledge. 
This verse clearly says that there were believing men and believing women in Mecca whose Islam was unknown, not only to the pagans but even to the Muslims of Medina. And Allah describes such practicers of taqiyah a: 'believing men' and `believing women'.
In short, these verses, traditions and incidents clearly show and demonstrate that if one is in danger of one's life because of his faith, then it is allowed to utter words against one's true belief of Islam, to save the life which is more important and that `lie' will not be counted against him.
as‑Sayid ar‑Radi says:
" … and we know that taqiyah affects only externally (i.e.' its effect is only on the tongue) and not internally (on the heart, spirit, soul). When someone forces another one to do something, (and that thing happens to be connected with heart) then the oppressor has no way of knowing that his wish has been complied with, except through some utterings by the tongue from which he will conclude that he has succeeded in changing the heart of the oppressed. Therefore, the best course of action at the time of taqiyah is to show the friendship with the unbelievers by words, to mix with them and live with them with good manners, but the heart must remain firmly with the previous feelings towards them, of hidden enmity and the belief of aloofness from them.
"And such a man (who finds himself in such a situation) should‑as far as possible‑use dissimulation and double‑entendre (i.e. words and sentences that admit two interpretations‑one correct, one wrong; the speaker intends correct meaning and the unbelievers take it to mean the other meaning).' 
 Qur’an, Surah 16 (an‑Nahl), verse 100
 Shah `Abdu 'l‑`Aziz Dehlawi, Tuhfa‑e‑Ithna‑'ashariyah, ch. 1, p. 368.
 `Allamah Wahidu'z‑Zaman Khan, Anwaru 'l‑lughah, Bangalor ed., para 20, p. 84.
 Qur’an, 49:14
 Qur’an, 63:1
 Qur’an, 5:32
 Qur’an, 2:195
 ar‑Razi, Tafsir Mafatihu 'l ghayb, old ed. vol. 5, pp. 746‑750.
 All Muslim sects agree that taqiyah is not only permissible but compulsory (wajib) in conditions like this. See, for example, Sahih Muslim with its Sharh by Nawawi which says:
The Islamic jurisprudents are agreed that if an oppressor comes looking for a man in hiding with intention to kill him, or looking for a thing given in trust, with an aim to usurp it. unlawfully, and he asks about him or it, then it is wajib on a person who knows about it to hide it and to deny any knowledge of him or it; and this is lawful ‑ rather wajib ‑ lie; because it is spoken to ward off an oppressor. (See its pages 106, 110, 200 and 325)
Imam Muslim has written a whole chapter on 'this theme, i.e., The chapter of unlawfulness of lie and description of lawful lies;
(a) al `Ayni, Umdatu 'l‑Qari Sharh Sahih al‑Bukhari, Egypt, vol. 5, p. 581; vol. 6, p. 352.
(b) Imam ar‑Razi, Tafsir Mafatihu 'l‑Ghayb, vol. 6, p. 164.
(c) `Allamah Wahidu 'z‑Zaman, Nuzulu 'l abrar min fiqhi 'n Nabii 'l‑Mukhtar vol. 3, p. 123.‑
 See the above references to appreciate that the Sunni scholars unanimously agree that taqiyah is allowed to save one's own life, honour or property.
 Imam ar‑Razi too has clearly described this contrast in his tafsir in the following words:
This points to the fact that (in these matters) consideration is given only to what is hidden iii the heart. A hypocrite who shows faith and hides disbelief is a disbeliever, while a believer who under compulsion shows disbelief and hides faith is a believer; and Allah better knows that is hidden in the hearts of all. (Vide Tafsir Mafatihu ‘l ghayb, Egypt, under verse 19:10).)
 Qur’an, 16:106.
(a) as‑Suyuti, Tafsir ad‑Durru 'l‑manthur, vol. 4, p. 132;
(b) ar‑Razi, Tafsir Mafatihu l‑ghayb;
(c) az‑Zamakhshari, Tafsir al‑Kashshaf, Beirut, vol. 2, p. 43c). Practically all books of Tafsir describe this event under this verse.
 Qur’an, 3;28‑29.
 as‑Suyuti, ad‑Durru l‑manthur, vol. 2, pp. 10‑17.
 ar‑Razi, Tafsir Mafatihu ‘l ghayb, Beirut, 3rd ed., vol. 7, p. 13.
 al‑Bukhari, as‑Sahib. Egypt ed., vol. 9, pp. 24‑25.
 as‑Sayid ar‑Radi, Tafsir Haqa'iqu 't‑ta'wil, vol. 5, p. 74.
 Qur’an, 2;173.
 Mulla `Ali Muttaqi, Kanzu l‑`ummal, Beirut, 5th ed., 1405/1985, vol. 3, p. 96, hadith no. 5665.
 al‑Kulayni, al‑Kafi, Tehran, 1388, vol. 2, p.174.
 Qur’an, 40:28
 `ubaydullah Amritsari, Arjahu 'l‑rnatalib, 2nd ed., p. 23
 Qur’an, 20.18; Tafsir al‑Baydawi, Egypt, vol. 1, pp. 112, 396 as quoted in Fulkun‑Najat, vol. 2, p. 103.
 as‑Suyuti, ad‑Durru 'l‑manthur, vol. 6, p. 77
 Qur’an, 48:25
 as‑Sayid ar‑Radi, op. cit, p. 77.