Narrated Anas bin Malik: The Prophet peace be upon him said, "There will be no town which Ad-Dajjal will not enter except Mecca and Medina, and there will be no entrance (road) (of both Mecca and Medina) but the angels will be standing in rows guarding it against him, and then Medina will shake with its inhabitants thrice (i.e. three earth-quakes will take place) and Allah will expel all the nonbelievers and the hypocrites from it." 

Sahih Bukhari, Vol 3, Book 30, No. 105

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