Abu Sa’eed (may Allah be pleased with him) narrated that :

the Prophet ﷺ said: “Whoever says, when he goes to his bed: ‘I seek forgiveness from Allah, [the Magnificent] the One whom there is none worthy of worship except for Him, the Living, the Sustainer, and I repent to Him (Astaghfiruallaha [Al-Azim] Alladhi La Ilaha Illa Huw, Al-Hayyul-Qayyum, Wa Atubu Ilaihi)’ three times, Allah shall forgive him his sins if they are like the foam of the sea, even if they were the number of leaves of the trees, even if they were the number of san particles of Alij, even if they were the number of the days of the world.”

حَدَّثَنَا صَالِحُ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا أَبُو مُعَاوِيَةَ، عَنِ الْوَصَّافِيِّ، عَنْ عَطِيَّةَ، عَنْ أَبِي سَعِيدٍ، رضى الله عنه عَنِ النَّبِيِّ ﷺ قَالَ " مَنْ قَالَ حِينَ يَأْوِي إِلَى فِرَاشِهِ أَسْتَغْفِرُ اللَّهَ الْعَظِيمَ الَّذِي لاَ إِلَهَ إِلاَّ هُوَ الْحَىَّ الْقَيُّومَ وَأَتُوبُ إِلَيْهِ . ثَلاَثَ مَرَّاتٍ غَفَرَ اللَّهُ ذُنُوبَهُ وَإِنْ كَانَتْ مِثْلَ زَبَدِ الْبَحْرِ وَإِنْ كَانَتْ عَدَدَ وَرَقِ الشَّجَرِ وَإِنْ كَانَتْ عَدَدَ رَمْلِ عَالِجٍ وَإِنْ كَانَتْ عَدَدَ أَيَّامِ الدُّنْيَا " .

قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ غَرِيبٌ لاَ نَعْرِفُهُ إِلاَّ مِنْ هَذَا الْوَجْهِ مِنْ حَدِيثِ الْوَصَّافِيِّ عُبَيْدِ اللَّهِ بْنِ الْوَلِيدِ .