Musnad Ahmad 32:1655

'Affan narrated to us, 'Abd al-Warith narrated to us, from Shu'ayb ibn al-Habhab, from Anas ibn Malik, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The Dajjal is wiped of the eye, written between his eyes is 'Kafir' (disbeliever)." He said: "Then he spelled it out: K-F-R. Every Muslim will read it."