Musnad Abu Ya'la al-Mawsili 3:280

Al-Hasan ibn 'Arafah narrated to us, Al-Mubarak ibn Sa'id—the brother of Sufyan al-Thawri—narrated to us, from Sa'id ibn Masruq, from Habib, from 'Abd Khayr al-Hamdani, who said: I heard 'Ali ibn Abi Talib saying upon this pulpit: "Shall I not inform you of the best of this nation after its Prophet?" He said: Then he mentioned Abu Bakr. He said: Then he said: "Shall I not inform you of the second?" He said: Then he mentioned 'Umar ibn al-Khattab. He said: Then he said: "If you wish, I would inform you of the third." He said: Then he remained silent. He said: Then we thought that he meant himself. Habib said: So I said to 'Abd Khayr, "Did you hear this from 'Ali?" He said: "Yes, by the Lord of the Ka'bah, or else may I be struck dumb."