(15) باب مَا يَدْعُو بِهِ إِذَا أَوَى إِلَى فِرَاشِهِ
It was narrated from 'Abdullah that:
whenever the Prophet (saas) went to his bed, he would put his hand - meaning his right hand - beneath his cheek then say: "Allahumma qini 'adhabaka yawm tab'athu - [or: tajma'u] - 'ibadaka (O Allah, save me from Your punishment on the Day when You resurrect - or gather - Your slaves)."
Reference: Sunan Ibn Majah 3877
In-book reference: Book 34, Hadith 51
English translation: Vol. 5, Book 34, Hadith 3877