Never should a believer kill another believer, except by mistake. If anyone kills a believer by mistake he must free one Muslim slave and pay compensation to the victim’s relatives, unless they charitably forgo it; if the victim belonged to a people at war with you but is a believer, then the compensation is only 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 relatives, and a believing slave set free. Anyone who lacks the means to do this must fast for two consecutive months by way of repentance to God: God is all knowing, all wise

If anyone kills a believer deliberately, the punishment for him is Hell, and there he will remain: God is angry with him, and rejects him, and has prepared a tremendous torment for him

So, you who believe, be careful when you go to fight in God’s way, and do not say to someone who offers you a greeting of peace, ‘You are not a believer,’ out of desire for the chance gains of this life- God has plenty of gains for you. You yourself were in the same position [once], but God was gracious to you, so be careful: God is fully aware of what you do