Sahih Bukhari
Afflictions and the End of the World
Volume: 009 / Book Number: 088 / Hadith Number: 240
Narrated Abu Bakra:
The Prophet said, "The terror caused by Al-Masih Ad-Dajjal will not enter Medina and at that time Medina will have seven gates and there will be two angels at each gate (guarding them).