Riyad as-Salihin 1586
Abu Sa'id Al-Khudri (May Allah be pleased with him) said:
The Prophet (ﷺ) said, "Every one who breaks a covenant will have a flag by his buttocks on the Day of Resurrection. It will be raised higher according to the nature of his breach. Behold, there will be no greater a sin with respect to breaking the covenant than that of a ruler who breaks his covenant with the Muslim masses." [Muslim] .
وعن أبي سعيد الخدري رضي الله عنه أن النبي صلى الله عليه وسلم قال ‏:‏ ‏
"‏ لكل غادر لواء عند استه يوم القيامة يرفع له بقدر غدره، ألا لا غادر أعظم غدرًا من أمير عامة‏"‏ ‏(‏‏(‏رواه مسلم‏)‏‏)‏‏.‏