Musnad Ahmad 830:29

Yahya ibn Sa'id narrated to us, from 'Uyaynah, he said: My father narrated to me, from Abu Bakrah, he said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "The Dajjal is blind in the left eye. Between his eyes is written 'Kafir' (disbeliever), which the illiterate and the literate will read."