The narrator states: On the day of Siffin, Sayyiduna Ali (may Allah be pleased with him) was leaning on al-Ashtar when Habis passed by, and Habis was one of the devout worshippers. Al-Ashtar said: O Commander of the Believers, Habis is with them; I know him, by Allah, to be a believer. Sayyiduna Ali (may Allah be pleased with him) said: "Then he is still a believer today."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3550