Hadith: No Prophet was sent but that he warned his people against the one-eyed liar

عن أنس بن مالك رضي الله عنه مرفوعاً: «ما من نبي إلا وقد أنذر أمته الأعور الكذاب، ألا إنه أعور، وإن ربكم - عز وجل - ليس بأعور، مكتوب بين عينيه ك ف ر»
[صحيح] - [متفق عليه]

Anas ibn Mālik (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: “No Prophet was sent but that he warned his people against the one-eyed liar. Beware! He is blind in one eye, and your Lord, Glorified and Exalted, is not. Between his eyes, the letters 'k', 'f', and 'r' are written (in Arabic).”
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

Each and every Prophet that was sent by Allah warned his people of the Anti-Christ because they knew that he will appear and how severe his temptation/tribulation is. The Prophets described some of his features to their people. This Hadīth mentions that he is one-eyed, and Allah is far Exalted above that. Another of his features is that the letters 'k', 'f', and 'r' are written between his eyes. These letters (in Arabic) form the word disbelief, which means disbelief.