Sayyiduna Ibn Umar (may Allah be pleased with them both) says: We heard about the Farewell Hajj while the Messenger of Allah (peace and blessings be upon him) was alive among us, and we did not think that it was a farewell from the Messenger of Allah (peace and blessings be upon him). Then the Messenger of Allah (peace and blessings be upon him) addressed us; he mentioned the Messiah (the Dajjal) and spoke about him at length, then mentioned about him whatever he wished, then said: "Indeed, Allah, the Mighty and Majestic, never sent any prophet except that he warned his nation about the Messiah (the Dajjal). Nuh (peace be upon him) warned his nation about him, then the prophets after him, one after another." Then he said: "Listen, whatever of his matter remains hidden from you" - the Messenger of Allah (peace and blessings be upon him) felt some hesitation in saying it - then he said: "Whatever of his matter remains hidden from you, let it not be hidden from you that your Lord is not one-eyed, while he (the Dajjal) will be blind in the right eye, as if his eye were a protruding grape. Listen! Have I conveyed?" Voices came from every side: Yes. He (peace and blessings be upon him) said three times: "O Allah, bear witness." Then he said: "Do not become disbelievers after me, some of you striking the necks of others."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13291