Hisnul Muslim 104

Before sleeping

اللَّهُمَّ قِنِي عَذَابَكَ يَوْمَ تَبْعَثُ عِبَادَكَ

Allaahumma qinee 'athaabaka yawma tab'athu 'ibaadaka.

O Allah, save me from Your punishment on the Day that You resurrect Your slaves. (Three times)(When the Prophet saw wanted to lie down to sleep, he used to place his right hand under his cheek and says this dua'.)