Musannaf Ibn Abi Shayba 37:361

Yazid ibn Harun narrated to us, from Humayd, from Anas, that the Prophet, may Allah bless him and grant him peace, said: "The Dajjal is blind in the right eye, upon it is a thick skin (tufra). Written between his eyes is 'Kafir' (disbeliever)."