Is it a condition to recite Surat Al-Mulk, Al-Waqi'ah, Ad-Dukhan, and As-Sajdah at night to attain their reward and achieve their objectives, or is it permissible to recite them at any time? And is it permissible to divide the recitation of a single surah into separate, spaced-out periods?

It was narrated concerning the virtue of Surat Al-Mulk that it saves one from the torment of the grave. As for the virtue of reading Surat Al-Waqi'ah for sustenance, the narrated hadith (definition) concerning it is weak, but it is permissible to act upon a weak hadith regarding the virtues of deeds under certain conditions. The hadiths about the virtue of Surat Ad-Dukhan are very weak or fabricated and are not to be acted upon. As for Surat As-Sajdah, it is Sunnah (definition) to recite it before sleeping, and it is not necessary to do so immediately upon going to sleep. The Sunnah did not specify a particular time for reciting these surahs, except for As-Sajdah, which is recommended to be recited before sleeping. The virtue is attained by reciting it during the day or night, even if intermittently.