Never should a believer kill another believer, unless by error. Anyone who kills a believer by error must set free a believing slave, and pay compensation to the victim’s family, unless they remit it as charity. If the victim belonged to a people who are hostile to you, but is a believer, then the compensation is 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 family, and a believing slave set free. Anyone who lacks the means must fast for two consecutive months, by way of repentance to God. God is All-Knowing, Most Wise.

The Holy Quran · An-Nisaa (The Women) · 4:92