Musnad Abu Ya'la al-Mawsili 3:206

Abu Bakr ibn Abi Shaybah narrated to us, Waki’ narrated to us, from Sufyan, from Jabir, from ‘Abdullah ibn Naji, from ‘Ali, who said: We were sitting with the Prophet, may Allah bless him and grant him peace, while he was sleeping, and we mentioned the Dajjal. He woke up with his face reddened and said: "Something other than the Dajjal is more feared by me for you than the Dajjal: misleading leaders."