1. There are certain surahs which have been prescribed to be recited at specific times during the night and day or during certain days of the week. It is mustahab for one to recite these surahs at their prescribed times.
e) One should recite Surah Mulk and Surah Sajdah before retiring to bed.
عن جابر : أن النبي صلى الله عليه و سلم كان لا ينام حتى يقرأ آلم تنزيل وتبارك الذي بيده الملك (ترمذي رقم 2892)
Hazrat Jaabir (radhiyallahu ‘anhu) reports that Rasulullah (sallallahu ‘alaihi wasallam) would not sleep until he recited Surah Sajdah and Surah Mulk.
وعن عبد الله بن مسعود رضي الله عنه قال من قرأ تبارك الذي بيده الملك كل ليلة منعه الله عز وجل بها من عذاب القبر وكنا في عهد رسول الله صلى الله عليه وسلم نسميها المانعة وإنها في كتاب الله عز وجل سورة من قرأ بها في ليلة فقد أكثر وأطاب رواه النسائي واللفظ له والحاكم وقال صحيح الإسناد (الترغيب والترهب للمنذري، الرقم: 2453)
It is reported that Hazrat Abdullah bin Mas’ood (radhiyallahu ‘anhu) said: “Whoever recites Surah Mulk every night, then by virtue of this surah Allah Ta‘ala will protect him from the punishment of the grave. During the time of Rasulullah (sallallahu ‘alaihi wasallam), we (the Sahaabah) would call this surah with the name Al Maani’ah (the one that protects one from the punishment of the grave). It is such a surah, that whoever recites it every night has certainly achieved a lot and has done good.”