Musnad Ahmad 27:1725

Ya'qub narrated to me, 'Asim ibn Muhammad narrated to us, from his brother 'Umar ibn Muhammad, from Muhammad ibn Zayd—meaning Abu 'Umar ibn Muhammad—who said: 'Abdullah ibn 'Umar said: We used to speak of the Farewell Pilgrimage, and we did not know that it was the farewell from the Messenger of Allah, may Allah bless him and grant him peace. When the Farewell Pilgrimage took place, the Messenger of Allah, may Allah bless him and grant him peace, delivered a sermon and mentioned the False Messiah (al-Masih ad-Dajjal), and he spoke at length about him. Then he said: "Allah has not sent a prophet but that he warned his nation about him. Noah, may Allah bless him and grant him peace, warned his nation about him, and the prophets after him, may Allah bless them and grant them peace, also did so. Beware, whatever is hidden from you regarding his affair, let it not be hidden from you that your Lord is not one-eyed. Beware, whatever is hidden from you regarding his affair, let it not be hidden from you that your Lord is not one-eyed."