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.
a) One should recite Surah Kaafiroon before sleeping
عن جبلة بن حارثة أن النبي صلى الله عليه و سلم قال : إذا أويت إلى فراشك فاقرأ: ( قل يا أيها الكافرون) حتى تمر بآخرها فإنها براءة من الشرك رواه الطبراني ورجاله وثقوا (مجمع الزوائد رقم 17033)
Hazrat Jabalah bin Haaritah (radhiyallahu ‘anhu) reports that Rasulullah (sallallahu ‘alaihi wasallam) said: “When you retire to bed, then recite Surah Kaafiroon till the end, for certainly reciting this surah is a means of being saved from shirk.”
عن فروة بن نوفل عن أبيه أن النبى صلى الله عليه وسلم قال لنوفل: اقرأ (قل يا أيها الكافرون) ثم نم على خاتمتها فإنها براءة من الشرك (ابو داود رقم 5057)
Hazrat Farwah bin Naufal (rahimahullah) reports from his father that Rasulullah (sallallahu ‘alaihi wasallam) said to Hazrat Naufal (radhiyallahu ‘anhu): “Recite Surah Kaafiroon and after completing its recitation, you should retire to bed, for certainly reciting this surah is a means of being saved from shirk.”