((يَقْرَأُ ﴿الم﴾ تَنْزِيلَ السَّجْدَة ِ، وَتَبَارَكَ الَّذي بِيَدِهِ الْمُلْكُ)).
The Prophet never used to sleep until he had recited Soorat As-Sajdah (chapter 32) and Soorat Al-Mulk (chapter 67).
At-Tirmidhi, An-Nasa'i. See also Al-Albani, Sahihul-Jami' As-Saghir 4/255.