Killing a Muslim in Three Cases

The Messenger of Allah (sal Allahu alaihi wa sallam) said: “It is not permitted to shed the blood of any Muslim who testifies that there is no God but Allah and that I am His Prophet, except in three cases: a soul for a soul (i.e. in the case of murder), the married man who commits adultery, and the one who forsakes his religion and abandons the Jama’ah.” [Bukhari]

Killing a Muslim is one of those sins for which Allah (subhana wa ta’ala) has promised a stay in Jahannum. It is a grievous crime permitted for only three reasons:

1. If a Muslim kills another then he is to be killed in return, or, if the heirs agree, pay 100 camels or its equivalent money to the heirs of the deceased in exchange for his life.

2. If a married Muslim commits adultery then his exemplary punishment should be a deterrent to all other married Muslims. Allah (subhana wa ta’ala) has allowed more than one marriage and also permitted divorce. There is, thus, no justification left to have relationships out of wedlock.

3. Apostasy is in fact the worst crime, because it ruins one’s never-ending Akhirah. An apostate who does not repent, if allowed to live, influences other people, in particular his children and family, to join him in apostasy. Apostasy is the ultimate in ingratitude to Allah (subhana wa ta’ala), denying His position, disavowing His favours, and living as though one owed nothing to Him - let alone everything. Thus, an apostate who does not repent is not allowed to live and spread his particular brand of poison around.
 
This hadith highlights the severity of these three crimes: murder, adultery, and apostasy. These are the only three things for which a Muslim’s (or ex-Muslim’s) life may be taken.