Muhammad ibn al-Munkadir told that he saw Jabir ibn Abdullah swearing by Allah that Ibn as-Sa'id was the Dajjal (Antichrist). I expressed my surprise by saying:You swear by Allah! He said: I heard Umar swearing to that in the presence of the Messenger of Allah (ﷺ), but the Messenger of Allah (ﷺ) did not make any objection to it

English translation · Sunan Abu Dawud