Takfir (Condemnation of a Muslim by another Muslim as a kafir)Takfir or the condemnation of a Muslim by another Muslim as a kafir is strictly prohibited in the Quran, the Hadith, and the writings of many eminent Muslim authorities.
According to the Quran, if a person says assalamu alaikum to us to indicate that he is a Muslim, we cannot say to him "you are not a believer.'' (4:94)
4:94 يَا أَيُّهَا الَّذِينَ آمَنُوا إِذَا ضَرَبْتُمْ فِي سَبِيلِ اللَّهِ فَتَبَيَّنُوا وَلَا تَقُولُوا لِمَنْ أَلْقَىٰ إِلَيْكُمُ السَّلَامَ لَسْتَ مُؤْمِنًا تَبْتَغُونَ عَرَضَ الْحَيَاةِ الدُّنْيَا فَعِندَ اللَّهِ مَغَانِمُ كَثِيرَةٌ كَذَٰلِكَ كُنتُم مِّن قَبْلُ فَمَنَّ اللَّهُ عَلَيْكُمْ فَتَبَيَّنُوا إِنَّ اللَّهَ كَانَ بِمَا تَعْمَلُونَ خَبِيرًا
Sahih International4:94 O you who have believed, when you go forth [to fight] in the cause of Allah , investigate; and do not say to one who gives you [a greeting of] peace "You are not a believer," aspiring for the goods of worldly life; for with Allah are many acquisitions. You [yourselves] were like that before; then Allah conferred His favor upon you, so investigate. Indeed Allah is ever, with what you do, Acquainted.
The second thing we learn from this verse is that if, from among a non-Muslim people, a person addresses us by assalamu alaikum, that is sufficient proof that he is a Muslim. When such incidents took place during the Holy Prophet's life-time, sometimes it was suspected by some Muslims that such a person was not sincere. But the Holy Prophet would say to them: ``Did you tear open his heart to see what was in it?''
Thirdly, the verse cited above goes on to say: "You yourselves were like this before.'' That is, you too embraced Islam in this way, so what was sufficient for you is sufficient for them.
In the hadith Ibn Umar related that the Holy Prophet said: If a Muslim calls another kafir, then if he is a kafir let it be so; otherwise, he [the caller] is himself a kafir.'' (Abu Dawud, Book of Sunna, edition published by Quran Mahal, Karachi, vol. iii, p. 484)
Abu Zarr reported that the Holy Prophet said: No man accuses another man of being a sinner, or of being a kafir, but it reflects back on him if the other is not as he called him.'' (Bukhari, Book of Ethics; Book 78, ch. 44)
The teaching contained in these hadith is meant to stop Muslims from dubbing each other as sinners and kafirs.
"Withhold [your tongues] from those who say `There is no god but Allah' --- do not call them kafir. Whoever calls a reciter of `There is no god but Allah' as a kafir, is nearer to being a kafir himself.'' (Tabarani, reported from Ibn Umar)
Call not the people of your Qibla [i.e. those who face the Ka`ba in Makka for prayer] as kafir.'' (Al-Nihaya of Ibn Athir, vol. iv, p. 187)
"Nothing expels a man from faith except the denial of that by which he entered into it [i.e. the Kalima].'' (Majma` az-Zawa'id, vol. i, p. 43)
"Three things are the basis of faith. [One is] to withhold from one who says `There is no god but Allah' --- do not call him kafir for any sin, nor expel him from Islam for any misconduct.'' (Abu Dawud, Book of Jihad, 15:33)
There are many other hadith prohibiting that the "people of the Qibla'' be dubbed as kafir. Such a great sin is it that the Holy Prophet issued the warning:
"Whoever attributes kufr [unbelief] to a believer, he is like his murderer.'' (Tirmizi, ch. Iman (Faith); see Arabic-Urdu edition cited earlier, vol. ii, p. 213. See also Bukhari, Book of Ethics; Book 78, ch. 44)
Takfir of Muslims is also prohibited in the standard, classical works of Islamic law (fiqh) and creed (`aqa'id) accepted by the Ahl as-Sunna.
"And among the doctrines of the Ahl as-Sunna is that none of the people of the Qibla can be called kafir.'' (Sharh `Aqa'id Nasfi, p. 121)
Regarding Imam Abu Hanifa, the founder of the Hanafi system of Islamic law, which has more followers than any other system in Islam, it is written: "He did not call as kafir anyone from among the people of the Qibla.'' (Sharh Mawaqif, fifth part)
He said: "Nothing expels a man from faith except the denial of that which made him enter it.'' (Rad al-Mukhtar, vol. iii, p. 310)
"It is extremely serious to expel a Muslim from the faith.''(Sharh Shifa, vol. ii, p. 500)
"A ruling of takfir against a Muslim should not be given if it is possible to interpret his words in a favourable manner.'' (Rad al-Mukhtar, Book of Jihad, ch. on Apostasy)
"As for statements of takfir found in books of rulings (fatwa), these are not proof if the authors are unknown and the arguments are missing, because in matters of faith, beliefs depend on conclusive proof, and the takfir of a Muslim is attended with troubles of all sorts.'' (Sharh Fiqh Akbar, by Mulla Ali Qari)
Allama Sayyid Jalal-ud-Din wrote: "The takfir of people of the Qibla is itself an act of unbelief.'' (Dala'il al-Masa'il)
Ibn Abu Hamra, a saint, wrote: "It has already been stated that the rule of the Ahl Sunna is that they do not call kafir, or consider as going to hell eternally, anyone who is of the people of the Qibla.''
"The Imams have made it clear that if there is any ground for not issuing takfir, a ruling of takfir should not be made, even if that ground is weak.'' (Raf al-ishtiba `an `ibarat al-ishtiba, p. 4, published in Egypt)
"Some prejudiced persons from the Asharis call the Hanbalis as kafir, and some Hanbalis call the Asharis as kafir. But their calling each other kafir is not right because the belief of the trustworthy Imams of the Hanafis, Shafi`is, Hanbalis, and the Asharis, is that none of the people of the Qibla can be called a kafir.'' (Miftah Dar as-Sa`ada wa Misbak as-Sayyida, vol i, p. 46)
"The generality of the theologians and the jurists are agreed that none of the people of the Qibla can be called a kafir.'' (Al-Mawaqif, printed in Cairo, p. 600)
The famous eighteenth century saint of Delhi, Khawaja Mir Dard (d. 1785 C.E.), wrote: "We do not call kafir anyone of the people of the Qibla, even though he may be following falsehood or novel beliefs in most matters, because the acceptance of the oneness of God, and the affirmation of the prophethood of Muhammad, and the turning to the Qibla, do not expel them from faith as such. So he would be of those who follow later inventions and falsehood from among the Muslims. The Holy Prophet said: `Withhold in the matter of the people of the Qibla, that you do not call them kafir'.'' (Ilm al-Kitab, p. 75)..