Sahih Muslim Book 31, Hadith Number 6024.

Chapter : The merits of ‘Abdullah b. Mas’ud and that of his mother (Allah be pleased with them).

Masruq reported: We used to go to Abdullah b. ‘Amr and talk to him, Ibn Numair said: One day we made a mention of Abdullah b. Mas’ud, whereupon he said: You have made mention of a person whom I love more than anything else. I heard Allah’s Messenger (may peace be upon him) as saying: Learn Qur’an from four persons: Ibn Umm ‘Abd (i.e. ‘Abdullah b. Mas’ud) he started from him-then Mu’adh b. Jabal and Ubayya b. Ka’b, then Salim the ally of Abu Hudhaifa.