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.
Sunan Abi Dawud Book 39, Hadith 41
← Previous Hadith Nafi' told that Ibn Umar used to say: I swear by Allah that I do not doubt that Antichrist is Ibn Sayyad.

Sunan Abi Dawud Book 39, Hadith 40 Next Hadith → We saw the last of Ibn Sayyad at the battle of the Harrah.

Sunan Abi Dawud Book 39, Hadith 42