وقعة صفين
In the Battle of Siffin, he made the characters who did not appear in the Battle of Camel and were condemned by Ali, to join the battle. During the Battle of Siffin, Mu'awiyah tried to seduce Hassan and sent Ubayd Allah ibn Umar to propose to Hassan to remove Ali from the caliphate and himself become the caliph, which was met with a negative response from Hassan. In Battle of Siffin, Hassan commanded the heart of Ali's corps. After the Arbitration and its aftermath, and the people's protest and reproach against Ali, Hasan, in a sermon strongly criticized the council of Arbitration, and the way it operated.