Musannaf Ibn Abi Shayba 37:380

Ya'la ibn 'Ubayd narrated to us, from al-A'mash, from Sulayman ibn Maysara, from Tariq ibn Shihab, from Hudhayfah, who said: "Indeed, some of the tribulation of the Dajjal had been fashioned while the Messenger of Allah, may Allah bless him and grant him peace, was still alive."