Hudhayfah reported: When the Prophet, peace and blessings be upon him, laid down at night, he would place his hand under his cheek and then say, “O Allah, in Your name I die and I live.” When the Prophet would awaken, he would say, “All praise is due to Allah, who has given us life after our death, and unto Him is the Resurrection.”
Source: Ṣaḥīḥ al-Bukhārī 5955
Grade: Sahih (authentic) according to Al-Bukhari
Ibn al-Qayyim said, “The Prophet would sleep when it was called for sleep, upon his right side and remembering Allah until sleep overtook his eyes.”
Source: al-Ṭibb al-Nabawī 1/179
عَنْ حُذَيْفَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا أَخَذَ مَضْجَعَهُ مِنْ اللَّيْلِ وَضَعَ يَدَهُ تَحْتَ خَدِّهِ ثُمَّ يَقُولُ اللَّهُمَّ بِاسْمِكَ أَمُوتُ وَأَحْيَا وَإِذَا اسْتَيْقَظَ قَالَ الْحَمْدُ لِلَّهِ الَّذِي أَحْيَانَا بَعْدَ مَا أَمَاتَنَا وَإِلَيْهِ النُّشُورُ
5955 صحيح البخاري كتاب الدعوات باب وضع اليد اليمنى تحت الخد الأيمن
قال ابن القيم فَيَنَامُ إِذَا دَعَتْهُ الْحَاجَةُ إِلَى النَّوْمِ عَلَى شِقِّهِ الْأَيْمَنِ ذَاكِرًا اللَّهَ حَتَّى تَغْلِبَهُ عيناه
1/179 الطب النبوي لابن القيم