Abu Sa'd al-Azdi narrates that he heard Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) say: "I received seventy surahs from the blessed mouth of the Messenger of Allah (peace and blessings be upon him)," and I had mastered them before Zayd bin Thabit became Muslim, when he was a boy with a lock of hair who played with the other boys.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8407