It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Learn the Qur'an from these four: Ubayy bin Ka'b, Mu'adh bin Jabal, Abdullah bin Mas'ud, and Salim the freed slave of Abu Hudhayfah."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8379