Apostasy is sinful, but it would only be punished in the hereafter. Muslims are not keepers over those who go astray to coerce them to accept Islam against their will. The duty of any Muslim is to convey the message and if somebody turns away, then the matter is between him and God. See also 3:20; 3:64; 3:144; 4:80; 5:92; 5:99; 5:105; 6:35; 6:66; 6:104; 6:107; 6:112; 6:149; 10:41; 10:99; 10:108; 24:54; 27:92; 30:52-53; 39:41; 50:45; 88:21-22; 109:6. There are other verses in the Quran which clearly envisage that an apostate is to be given an opportunity until his natural death to return to the fold of Islam, and if he doesn't his punishment is in the next life, not here: Quran 2:217: "…they will not cease fighting with you until they turn you back from your religion, if they can; and whoever of you turns back from his religion, then he dies while an unbeliever-- these it is whose works shall go for nothing in this world and the hereafter, and they are the inmates of the fire; therein they shall abide." The Arabic word that is used here is "fayamut" implies a person dying on his own and not being slain. Quran makes that clear distinction in verse 3:144 which uses two words "matta" (dies) and "qutila" (slain) together [both matta and fayamuth are derived from the same word 'moth' meaning death].
There are verses which say:
[3.85] And whoever desires a religion other than Islam, it shall not be accepted from him, and in the hereafter he shall be one of the losers.
[3.86] How shall Allah guide a people who disbelieved after their believing and (after) they had borne witness that the Apostle was true and clear arguments had come to them; and Allah does not guide the unjust people.
[3.87] (As for) these, their reward is that upon them is the curse of Allah and the angels and of men, all together.
[3.88] Abiding in it; their chastisement shall not be lightened nor shall they be respited.
[3.89] Except those who repent after that and amend, then surely Allah is Forgiving, Merciful.
[3.90] Surely, those who disbelieve after their believing, then increase in unbelief, their repentance shall not be accepted, and these are they that go astray.
[3.91] Surely, those who disbelieve and die while they are unbelievers, the earth full of gold shall not be accepted from one of them, though he should offer to ransom himself with it, these it is who shall have a painful chastisement, and they shall have no helpers.
In these verses, Quran clearly offers repentance to apostates and in the absence of which, a painful punishment awaits them in the next world. No mention is made of punishment in this world.
In Hadith literature, only those apostates are to be killed who are either waging a war against Muslims or who have joined the enemy camp. Bukhari has two chapters devoted to the issue of Apostasy. The first chapter is called “Kitab al-muaribin min ahl al-fufr wal’ridda (the book of those who fight (against the Muslims) from among the unbelievers and the apostates). The second chapter is called “kitaab istibat al-muanideen wal’murtadeen wa qital-i-him” (the book of calling to repentance to the enemies and the apostates and fighting with them.) It is obvious that both of these chapters refer to apostates who have become enemies of Muslims and the punishment for apostasy is not for simple conversion from faith. Those who quote the Hadith, “Whoever changes his religion, kill him,” forget that the same Hadith can apply to non-believers converting to Islam!
There is not a single Hadith according to which Prophet Muhammad ordered the killing of a person just because he had converted out of Islam. In fact, there are two separates Ahadiths (plural of Hadith) in which two people converted out of Islam and they were not punished. One is the example of a person who had developed a flu after becoming a Muslim and thought that his sickness was due to his conversion (Bukhari 94:47). The other example is that of a scribe who converted to Christianity (Bukhari 61:25).
The same is true about ‘fiqh’ where an apostate has to be ‘kafir-un harabiyy-un’ (unbeliever at war) to be executed. For reference see al-Marghinani’s al-Hidaya. Al Marghinani was the great Hanafi jurist, born in 1135 AD. His book has been recognized as the primary source for many ‘figh’ related issues where guidance cannot be found in either the Quran or the Hadith. Jurists who thought otherwise were merely relying on opinions and had little if anything from Quran and Hadith to support their point of view.
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