Tafsir of Al-Anfal 8:71

{And if they intend to betray you} By breaking the covenant of Islam they pledged to you, reverting to apostasy, and preferring the religion of their forefathers.

{Then they have already betrayed Allah before} Through their disbelief in Him and by violating the covenant taken from every rational being.

{So He gave [you] power over them} Just as you witnessed on the day of Badr; He will grant you power over them again if they repeat their betrayal. It is also said that the "betrayal" refers to withholding the ransom they had guaranteed.

{Indeed, those who have believed and emigrated and fought with their wealth and their lives in the cause of Allah, and those who gave shelter and aided - they are allies of one another. But those who believed and did not emigrate - for you there is no guardianship of them until they emigrate. And if they seek help of you for the religion, then you must help, except against a people between whom and yourselves is a treaty. And Allah is Seeing of what you do.}