سورة An-Nisa ( The Women ) - الآية 92

It is not for a believer to take a believer's life except by mistake; and he who kills a believer by mistake should free a slave who is a believer, and pay blood-money to the victim's family unless they forego it as an act of charity. If he belonged to a community hostile to you but was himself a believer, then a slave who is a believer should be freed. In case he belonged to a people with whom you have a treaty, then give blood-money to his family and free a believing slave. But he who has no means (to do so) should fast for a period of two months continuously to have his sins forgiven by God, and God is all-knowing and all-wise.