Musnad Ahmad 28:291

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Sulayman, I heard Abu Wa’il narrating from Masruq, from ‘Abdullah ibn ‘Amr, from the Prophet, peace and blessings of Allah be upon him, who said: "Seek to learn the recitation of the Qur’an from four: from ‘Abdullah ibn Mas‘ud, Salim the freed slave of Abu Hudhayfah, Mu‘adh ibn Jabal, and Ubayy ibn Ka‘b." He said: And he said: "The Messenger of Allah, peace and blessings of Allah be upon him, was neither one who used foul language nor one who sought to use foul language." He said: And the Messenger of Allah, peace and blessings of Allah be upon him, said: "Indeed, among the most beloved of you to me are those of you with the best character."