Musnad Ahmad 32:1206

Rawh narrated to us, Sa'id narrated to us, from Qatadah, that Anas ibn Malik informed them that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, between his eyes is written 'K-F-R'—meaning disbeliever (Kafir)—which every believer will read, whether literate or illiterate."