Abu Darda' reported Allah's Apostle (ﷺ) as saying
If anyone learns by heart the first ten verses of the Surah al-Kahf, he will be protected from the Dajjal.
This hadith has been transmitted by Qatada with the same chain of transmitters. But Shu'ba (one of the narrators) said
At the end of Surah al-Kahf, but Hammam said: At the beginning of Surah al-Kahf.
Ubayy b. Ka'b said
Allah's Messenger (ﷺ) said: O Abu' al-Mundhir, do you know the verse from the Book of Allah which, according to you, is the greatest? I said: Allah and His Apostle (ﷺ) know best. He again said: Abu'l-Mundhir, do you know the verse from the Book of Allah which, according to you, is the greatest? I said: Allah, there is no god but He, the Living, the Eternal. Thereupon he struck me on my breast and said: May knowledge be pleasant for you, O Abu'l-Mundhir!