Section 13  

[Nisa 4:92] It is not rightful for a Muslim to kill another Muslim, unless it occurs by mistake; and the one who mistakenly kills a Muslim must set free a Muslim slave and pay blood-money to the family of the slain, except if they forego it; and if the victim is of a people who are hostile to you, and the killer is a Muslim, then only the setting free of a Muslim slave (is obligatory); and if the victim is from a people between whom and you there is a treaty, then blood-money must be paid to his family and the setting free of a Muslim slave; therefore one who has no means must fast for two consecutive months; this is his penance before Allah; and Allah is All Knowing, Wise.

[Nisa 4:93] And whoever slays a Muslim on purpose, his reward will be hell - to remain in it for ages - and Allah has wreaked wrath upon him and has cursed him and kept prepared a terrible punishment for him.

[Nisa 4:94] O People who Believe! When you go forth to fight in holy war, make a proper study, and do not say to the one who greets you, "You are not a Muslim," - you seek the means of this worldly life; so with Allah are the bounties in plenty; you too were like this before, then Allah bestowed His favour on you, therefore you must make a proper study; indeed Allah knows whatever you do.