Musnad Ahmad 5:316

Yahya ibn Adam narrated to us, Malik ibn Mighwal narrated to us, from Habib ibn Abi Thabit, from 'Abd Khayr, from 'Ali; and from al-Sha'bi, from Abu Juhayfah, from 'Ali; and from 'Awn ibn Abi Juhayfah, from his father, from 'Ali, that he said: "The best of this nation after its Prophet is Abu Bakr, and the best of it after Abu Bakr is 'Umar. And if I wished, I would have named the third."