What to say before sleeping — Du'a 12

يَقرَأُ ﴿الم﴾ تَنزِيلَ السَّجدَة ِ، وَتَبَارَكَ الَّذي بِيَدِهِ المُلكُ

English meaning

The Prophet never used to sleep until he had recited Soorat As-Sajdah (chapter 32) and Soorat Al-Mulk (chapter 67).