Chapter 33: The Book ofJihadand Expeditions
It is narrated on the authority of Abu Sa' id that the Messenger of Allah (ﷺ) said: On the Day of Judgment there will be a flag for every person guilty of the breach of faith. It will be raised in proportion to the extent of his guilt; and there is no guilt of treachery more serious than the one committed by the ruler of men.
Sahih Muslim 1738b