So when you meet in battle those who disbelieve, then smite their necks until when you have overcome them, make them prisoners, and afterwards either set them free as a favour or let them ransom themselves until the war terminates. That is the command. And if Allah had pleased He could certainly have exacted what is due from them (without you), but (thus it is ordained) that He may try some of you by means of others. As for those who are slain in the way of Allah, He will by no means allow their deeds to perish.