(20) باب ذِكْرِ الدَّجَّالِ وَصِفَتِهِ وَمَا مَعَهُ
Anas b. Malik reported that Allah's Messenger (ﷺ) said:
There would be written three letters k. f. r., i. e. Kafir, between the eyes of the Dajjal.
Reference: Sahih Muslim 2933 b
In-book reference: Book 54, Hadith 128
USC-MSA web (English) reference(deprecated numbering scheme): Book 41, Hadith 7008