Musannaf Ibn Abi Shaybah

Hazrat Muawiyah bin Qurrah (may Allah have mercy on him) narrates that Hasan (may Allah have mercy on him) and I were sitting and talking when Hasan (may Allah have mercy on him) mentioned Hazrat Ali (may Allah be pleased with him) and said: He (may Allah be pleased with him) was the most upright among the people and the one who would straighten the religion of the people when crookedness would appear in it.