It was narrated that Abu Sa’eed bin Mu’alla said: “The Messenger of Allah said to me: ‘Shall I not teach you the greatest Surah in the Quran before I leave the masjid?’ Then the Prophet went to leave, so I reminded him, and he said: Al-hamdulillahi Rabbil-Alameen (All the praise is to Allah, the Lord of all that exists). It is the Seven Oft-Recited Verses, and it is the Grand Quran that has been given to me.’”
(Sunan Ibn Majah 3785, Book 33, Hadith 130)