One should recite the musabbihaat (i.e. those surahs that begin with the words of tasbeeh) before sleeping. These Surahs are Surah Bani Israa’eel, Surah Hadeed, Surah Hashr, Surah Saff, Surah Jumuah, Surah Taghaabun and Surah A’ala.
عن العرباض بن سارية رضي الله عنه : أن النبي صلى الله عليه و سلم كان لا ينام حتى يقرأ المسبحات ويقول فيها آية خير من ألف آية (ترمذي رقم 3406)
Hadhrat Irbaadh bin Saariyah (Radhiyallahu Anhu) reports that Rasulullah (Sallallahu Alaihi Wasallam) would not sleep until he recited the musabbihaat, and he would say “In these surahs, there is a verse greater than a thousand verses.”