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He reported the Prophet (ﷺ) as saying, “If anyone who is about to sleep on his bed lies on his right side, then recites ‘Say, He is God, One’ a hundred times, the Lord will say to him on the day of resurrection, ‘My servant, enter paradise to your right’.” Tirmidhī transmitted it, saying this is a hasan gharīb tradition.
Source: sunnah.com
Other translations
Arabic
وَعَنْ أَنَسٍ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: " مِنْ أَرَادَ أَنْ يَنَامَ عَلَى فِرَاشِهِ فَنَامَ عَلَى يَمِينِهِ ثُمَّ قَرَأَ مِائَةَ مَرَّةٍ (قل هُوَ الله أحد) إِذا كَانَ يَوْم الْقِيَامَةِ يَقُولُ لَهُ الرَّبُّ: يَا عَبْدِي ادْخُلْ عَلَى يَمِينِكَ الْجَنَّةَ ". رَوَاهُ التِّرْمِذِيُّ وَقَالَ: هَذَا حَدِيثٌ حَسَنٌ غَرِيبٌ
sunnah.com