Musnad Abu Ya'la al-Mawsili 1:33

Abu Musa Muhammad ibn al-Muthanna and Ahmad ibn Ibrahim al-Dawraqi narrated to us, they said: Rawh narrated to us, Sa'id ibn Abi 'Aruba narrated to us, from Abu al-Tayyah, from al-Mughira ibn Subay', from 'Amr ibn Hurayth, from Abu Bakr al-Siddiq. And in the hadith of Abu Musa, he said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Indeed, the Dajjal will emerge from a land in the east called Khurasan. He will be followed by peoples whose faces are like hammered shields."