Musannaf Ibn Abi Shayba 37:600

Zayd ibn al-Hubab narrated to us, he said: al-‘Ala’ ibn al-Minhal narrated to me, he said: So-and-so narrated to me, he said: I heard al-Zuhri at al-Rusafah saying: "O Allah, ‘Ali was indeed sincere, and he was correct regarding ‘Uthman. Had they not obtained the document, they would have turned back."