121. Surah to be recited before going to sleep

Jabir (RA) said, Rasulullah (ﷺ) would not sleep without reciting Surah Sajdah and Surah Mulk. [1] Ayesha (RA) said, "The Messenger of Allah (ﷺ), would not sleep without reciting Surah Bani Isra'il and Surah Zumar." In another hadith, Ayesha (RA) said that the Prophet (ﷺ) used to recite Surah Sajdah and Surah Zumar every night. [2]

Reference[1] Sahih (Albani). Tirmidhi: 3404 [2] Sahih (Albani). Tirmidhi: 2920