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 a believer; but (If it so happens) by mistake, (Compensation is due): If one (so) kills a believer, it is ordained that he should free a believing slave, and pay compensation to the deceased's family, unless they remit it freely. If the deceased belonged to a people at war with you, and he was a believer, the freeing of a believing slave (Is enough). If he belonged to a people with whom ye have treaty of Mutual alliance, compensation should be paid to his family, and a believing slave be freed. For those who find this beyond their means, (is prescribed) a fast for two months running: by way of repentance to Allah: for Allah hath all knowledge and all wisdom.