Ibn Mas'ud, Ibn 'Umar and Anas (May Allah be pleased with them) said:
The Prophet (ﷺ) said, "For every one who breaks his covenant, there will be a (huge) flag on the Day of Resurrection and it will be said: 'This flag proclaims a breach of covenant by so-and-so."'[Al-Bukhari and Muslim].
App reference: Book 18, Hadith 75
Arabic/English book reference: Book 18, Hadith 1585