Surah 8:71
"But if they intend to betray you, they have already betrayed God before (that). So He has given (you) power over them. God is knowing, wise."
8.71 – So He has given (you) power over them
About the treatment of captives taken in the battle, the Quran tells the prophet (see v. 70) that Allah has given him power over them. This message seems to contradict many other parts of the Quran where the messenger has no permission or power to hurt others.
- from The Quran with Christian Commentary: A Guide to Understanding the Scripture of Islam