Musannaf Ibn Abi Shayba 27:787

Muhammad ibn Bishr narrated to us, he said: Mis'ar narrated to us, from Sa'd ibn Ibrahim, from his father, from Abu Bakrah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "The terror of the False Messiah (Al-Masih ad-Dajjal) will not enter Medina. It will have seven gates on that day, and at every gate there will be two angels."