سورة An-Nisa ( The Women ) - الآية 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.