مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4342
Musnad of Abdullah bin Mas'ood
It was narrated that Ibn Mas'ood said: I learned seventy soorahs from the lips of the Messenger of Allah (ﷺ) and no one else was with me when I learned them.
Musnad Ahmad 4372Its isnad is hasan]