(Imām Bukhārī narrates): 'Abdullāh ibn Maslamah narrated to us, from Imām Mālik, from Sumayy, the freed slave of Abū Bakr, from Abī Sālih, from Abū Hurairah, he narrates that the Messenger of Allāh ﷺ said:

When the imām says "Ghayril-maghdūbi 'alaihim wa lād-dāllīn," you say "Āmīn," for whoever's saying coincides with the saying of the angels, his past sins will be forgiven.

Sumayy has been corroborated by Muhammad ibn 'Amr, from Abī Salamah, from Abū Hurairah, from the Prophet ﷺ. And Nu'aim al-Mujmir has also corroborated Sumayy, from Abū Hurairah, may Allāh be pleased with him.