Abu Sa’id bin al-Mu’alla (RA) reported, “I was praying when the Messenger of Allah ﷺ passed by me and called me. I didn’t come to him until I finished praying. Then I came to him and he said, “What prevented you from coming? Didn’t Allah say, ‘O you who believe, respond to Allah and to the Messenger when he calls you’?” Then he said, “I shall teach you the greatest sūrah in the Qur’an before I leave.” The Messenger of Allah ﷺ started to leave so I reminded him of it.” Mu’āth said, “Shu’bah narrated this to us from Khubayb, who heard from Hafs, who heard from Abu Sa’id, a man from the companions of the Prophet ﷺ, and he said, “It is ‘Alhamdu lillāhi Rabbil ‘Ālameen (i.e., Sūrah Al-Fātiḥah) which is As-Sab’ Al-Mathāni (i.e., the seven oft-repeated āyāt).” Reference: Sahih al-Bukhari 4474