مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3576
Musnad of Abdullah bin Mas'ood
It was narrated from 'Asim with his isnad. He said: Abu Bakr brought him a hollowed out stone and he milked (the sheep) into it, then he drank and Abu Bakr drank and I drank. I came to him after that and said: Teach me some of this Qur'an. He said: “You are a boy and you will learn (later).” And I learned seventy soorahs from his lips.
Musnad Ahmad 3599Its isnad is hasan]