Putting right hand under right cheek on sleeping

Narrated Hudhaifa:

When the Prophet went to bed at night, he would put his hand under his cheek and then say, "Allahumma bismika amutu wa ahya," and when he got up, he would say, "Al-Hamdu lil-lahi al-ladhi ahyana ba'da ma amatana, wa ilaihi an-nushur."

حَدَّثَنِي مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ عَبْدِ الْمَلِكِ، عَنْ رِبْعِيٍّ، عَنْ حُذَيْفَةَ ـ رضى الله عنه قَالَ كَانَ النَّبِيُّ ﷺ إِذَا أَخَذَ مَضْجَعَهُ مِنَ اللَّيْلِ وَضَعَ يَدَهُ تَحْتَ خَدِّهِ ثُمَّ يَقُولُ " اللَّهُمَّ بِاسْمِكَ أَمُوتُ وَأَحْيَا ". وَإِذَا اسْتَيْقَظَ قَالَ " الْحَمْدُ لِلَّهِ الَّذِي أَحْيَانَا بَعْدَ مَا أَمَاتَنَا وَإِلَيْهِ النُّشُورُ ".