Sahih Muslim Book 41, Hadith Number 7009.
Chapter : Account of the Dajjal and his features and what would be along with.
Anas b. Malik reported that Allah’s Messenger (may peace be upon him) said: Dajjal is blind of one eye and there is written between his eyes the word “Kafir”. He then spelled the word as k.f.r, which every Muslim would be able to read.