Sahih Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Volume: 005 / Book Number: 059 / Hadith Number: 519
Narrated Abu Imran:
Anas looked at the people wearing Tailsans (i.e. a special kind of head covering worn by Jews in old days). On that Anas said, "At this moment they (i.e. those people) look like the Jews of Khaibar."