(Imām Bukhārī narrates): 'Abdullāh ibn Yūsuf narrated to us, he said: Imām Mālik informed us, from Abī al-Zinād, from al-A'raj, from Abū Hurairah, may Allāh be pleased with him, that the Messenger of Allāh ﷺ said:

When any one of you says "Āmīn," and the angels also say "Āmīn" in the sky, and the saying of one of the two coincides with the other, then his past sins are forgiven.