Musnad Ahmad 830:68

Sulayman ibn Dawud al-Hashimi narrated to us, Ibrahim ibn Sa'd informed us, from his father, from his father, from Abu Bakrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The terror of the False Messiah (al-Masih al-Dajjal) shall not enter Medina. It will have seven gates on that day, and at every gate of them there will be two angels."