سورة An-Nisa ( The Women ) - الآية 92

A believer may not kill another believer, unless it is by mistake. Anyone who kills a believer by mistake should set free a believing slave, and pay blood-money to his family, unless they remit it in charity. If he belongs to a people that are hostile to you but is a believer, then a believing slave is to be set free. And if he belongs to a people with whom you have a treaty, the blood-money is to be paid to his family and a believing slave is to be set free. He who cannot afford [to pay the blood-money], must fast two successive months as a penance from Allah, and Allah is all-knowing, all-wise.