Musannaf Ibn Abi Shayba 3:1079

Ibn ‘Ulayyah narrated to us, from Ayyub, from ‘Amr ibn Salamah, who said: We were at a watering place, and travelers would pass by us returning from the Prophet (ﷺ). I would draw near to them and listen until I memorized much of the Qur’an. The people were waiting for the conquest of Makkah to embrace Islam. When it was conquered, a man would come to him and say, "O Messenger of Allah, I am a delegate of such-and-such tribe, and I have come to you with their Islam." My father went with the Islam of his people. When he returned, the Messenger of Allah (ﷺ) said, "Put forward the one among you who has memorized the most Qur’an." He said: They looked, and I had learned a great deal of the Qur’an. They did not find anyone among them who had memorized more Qur’an than me, so they put me forward, and I was a young boy, and I led them in prayer.