Silsilat al-Ahadith al-Sahihah

Umar bin Thabit Ansari says that a companion of the Messenger of Allah narrated to me that one day the Prophet Muhammad (peace and blessings be upon him) warned them about the Dajjal, saying: "Know that no one can see his Lord before dying, and between the eyes of this Dajjal will be written 'K F R'. Every person who dislikes his actions will be able to read these words."