Translation:

71. But if they have treacherous designs against thee (o apostle!) they have already been in treason against Allah and so hath He given (thee) power over them and Allah is He who hath (full) knowledge and wisdom.

Notes (Tafseer)

1238. If the kindness shown to them is abused by the prisoners of war when they are released, it is not a matter for discouragement to those who showed the kindness. Such persons have in their treachery shown already their treason to Allah, in that they took up arms against Allah's Prophet, and sought to blot out the pure worship of Allah. The punishment of defeat, which opened the eyes of some of their comrades, evidently did not open their eyes. But Allah knows all, and in His wisdom will order all things for the best. The Believers have done their duty in showing such clemency as they could in the circumstances of war. For them "Allah sufficeth" (viii. 62).