Yahya related to me from Malik from Abu Ubayd, the mawla of Sulayman ibn Abd al-Malik, from Ata ibn Yazid al-Laythi that Abu Hurayra said, "Whoever says 'Glory be to Allah' (Subhana'llah) thirty- three times and 'Allah is Greater' (Allahu akbar) thirty-three times and 'Praise be to Allah' (al-hamdu lillah) thirty-three times, and seals the hundred with 'There is no god but Allah, alone without any partner. The Kingdom and praise belong to Him and He has power over everything' (La ilaha illa'llah, wahdahu la sharika lah, lahu'l mulku wa lahu'l hamd, wa huwa ala kulli shay'in qadir) after every prayer will have his wrong actions forgiven him even if they are abundant as the foam on the sea."


وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي عُبَيْدٍ، مَوْلَى سُلَيْمَانَ بْنِ عَبْدِ الْمَلِكِ عَنْ عَطَاءِ بْنِ يَزِيدَ اللَّيْثِيِّ، عَنْ أَبِي هُرَيْرَةَ، أَنَّهُ قَالَ مَنْ سَبَّحَ دُبُرَ كُلِّ صَلاَةٍ ثَلاَثًا وَثَلاَثِينَ وَكَبَّرَ ثَلاَثًا وَثَلاَثِينَ وَحَمِدَ ثَلاَثًا وَثَلاَثِينَ وَخَتَمَ الْمِائَةَ بِلاَ إِلَهَ إِلاَّ اللَّهُ وَحْدَهُ لاَ شَرِيكَ لَهُ لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ وَهُوَ عَلَى كُلِّ شَىْءٍ قَدِيرٌ غُفِرَتْ ذُنُوبُهُ وَلَوْ كَانَتْ مِثْلَ زَبَدِ الْبَحْرِ ‏"‏ ‏.‏
USC-MSA web (English) reference : Book 15, Hadith 22
Arabic reference : Book 15, Hadith 494