Surah Al- Kahf
Hadrat Ali Radiyallahu 'anhu narrates that Rasulullah Sallallahu 'alaihi wasallam said:
He who recites Surah Al-Kahf on Friday, will be protected from all kinds of trials for eight days, and if Dajjal appears, (during these eight days) he would be even saved from him.
(Tafsir ibne-Kathir)