Sahih Bukhari Volume 004, Book 055, Hadith Number 574.
Narated By Mujahid : That when the people mentioned before Ibn 'Abbas that the Dajjal would have the word Kafir, (i.e. unbeliever) or the letters Kafir (the root of the Arabic verb 'disbelieve') written on his forehead, I heard Ibn 'Abbas saying, "I did not hear this, but the Prophet said, 'If you want to see Abraham, then look at your companion (i.e. the Prophet) but Moses was a curly-haired, brown man (who used to ride) a red camel, the reins of which was made of fires of date-palms. As if I were now looking down a valley."