سورة An-Nisa ( The Women ) - الآية 92

It is not for a believer to kill a believer except by mistake; and whosoever kills a believer by mistake, he must set free a believing slave and submit compensation (blood money) to the deceased's family unless they remit it. If the deceased belonged to a people at war with you and he was a believer, the freeing of a believing slave (is prescribed); and if he belonged to a people with whom you have a treaty of mutual alliance, then compensation (blood money) must be paid to his family, and a believing slave must be freed. And whoso finds this beyond his means, he must fast for two consecutive months in order to seek repentance from Allah. And Allah is Ever All-Knowing, All-Wise.