So when you meet those who disbelieve [in battle], strike [their] necks until, when you have inflicted slaughter upon them, then secure [their] bonds, and either [confer] favor afterwards or ransom [them] until the war lays down its burdens. That [is the command]. And if Allāh had willed, He could have taken vengeance upon them [Himself], but [He ordered armed struggle] to test some of you by means of others. And those who are killed in the cause of Allāh - never will He waste their deeds.

Sahih International