An-Nisa 4:92 وما كان لمومن ان يقتل مومنا الا خطا ومن قتل مومنا خطا فتحرير رقبة مومنة ودية مسلمة الى اهله الا ان يصدقوا فان كان من قوم عدو لكم وهو مومن فتحرير رقبة مومنة وان كان من قوم بينكم وبينهم ميثاق فدية مسلمة الى اهله وتحرير رقبة مومنة فمن لم يجد فصيام شهرين متتابعين توبة من الله وكان الله عليما حكيما ٩٢

Never should a believer kill another believer, except by mistake. If anyone kills a believer by mistake he must free one Muslim slave and pay compensation to the victim’s relatives, unless they charitably forgo it; if the victim belonged to a people at war with you but is a believer, then the compensation is only to free a believing slave; if he belonged to a people with whom you have a treaty, then compensation should be handed over to his relatives, and a believing slave set free. Anyone who lacks the means to do this must fast for two consecutive months by way of repentance to God: God is all knowing, all wise.