Musnad Ahmad 1:12

Rawh narrated to us, he said: Ibn Abi Arubah narrated to us, from Abu al-Tayyah, from al-Mughirah ibn Subay', from 'Amr ibn Hurayth, from Abu Bakr al-Siddiq, who said: The Messenger of Allah (peace and blessings of Allah be upon him) narrated to us: "The Dajjal will emerge from a land in the East called Khurasan. He will be followed by peoples whose faces are like hammered shields."