When the Messenger of Allah ﷺ wanted to go to sleep, he put his right hand under his cheek and would then say three times: O Allah, guard me from Thy punishment on the day when Thou raisest up Thy servants.
عَنْ حَفْصَةَ زَوْجِ النَّبِيِّ ﷺ أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ إِذَا أَرَادَ أَنْ يَرْقُدَ وَضَعَ يَدَهُ الْيُمْنَى تَحْتَ خَدِّهِ ثُمَّ يَقُولُ اللَّهُمَّ قِنِي عَذَابَكَ يَوْمَ تَبْعَثُ عِبَادَكَ ثَلاَثَ مِرَارٍ