Surah Muhammad · Ayah 4

فَإِذَا لَقِيتُمُ ٱلَّذِينَ كَفَرُوا۟ فَضَرْبَ ٱلرِّقَابِ حَتَّىٰٓ إِذَآ أَثْخَنتُمُوهُمْ فَشُدُّوا۟ ٱلْوَثَاقَ فَإِمَّا مَنًّۢا بَعْدُ وَإِمَّا فِدَآءً حَتَّىٰ تَضَعَ ٱلْحَرْبُ أَوْزَارَهَا ۚ ذَٰلِكَ وَلَوْ يَشَآءُ ٱللَّهُ لَٱنتَصَرَ مِنْهُمْ وَلَٰكِن لِّيَبْلُوَا۟ بَعْضَكُم بِبَعْضٍۢ ۗ وَٱلَّذِينَ قُتِلُوا۟ فِى سَبِيلِ ٱللَّهِ فَلَن يُضِلَّ أَعْمَٰلَهُمْ

Fa-izaa laqeetumul lazeena kafaroo fadarbar riqaab, hattaaa izaa askhan tumoohum fashuddul wasaaq, fa immaa mannnam ba'du wa immaa fidaaa'an hattaa tada'al harbu awzaarahaa; zaalika wa law yashaaa'ul laahu lantasara minhum wa laakil laiyabluwa ba'dakum biba'd; wallazeena qutiloo fee sabeelil laahi falany yudilla a'maalahum

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 Allah 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 Allah - never will He waste their deeds.