Musannaf Ibn Abi Shayba 38:184

Yahya ibn Adam narrated to us, he said: Hammad ibn Zayd narrated to us, from Ibn ‘Awn, from al-Hasan, who said: When ‘Ali appointed the two arbitrators, the people of al-Harura’ said: "You have done nothing but join these people." So they went out. Then Iblis came to them and said: "Where were these people whom we left as Muslims? What an evil opinion we held! And if they were [as they were], it is necessary for us to call out to them." Al-Hasan said: So Abu al-Hasan (Ali) sprang upon them and cut them down completely.