عَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ: ((مَنْ سَبَّحَ اللَّهَ فِي دُبُرِ كُلِّ صَلَاةٍ ثَلَاثًا وَثَلَاثِينَ، وَحَمِدَ اللَّهَ ثَلَاثًا وَثَلَاثِينَ وَكَبَّرَ اللَّهَ ثَلَاثًا وَثَلَاثِينَ، فَتِلْكَ تِسْعٌ وَتِسْعُونَ، ثُمَّ قَالَ تَمَامَ الْمِائَةِ لَا إِلَهَ إِلَّا اللَّهُ وَحْدَهُ لَا شَرِيكَ لَهُ، لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ وَهُوَ عَلَى كُلِّ شَيْءٍ قَدِيرٌ، غُفِرَ لَهُ خَطَايَاهُ وَإِنْ كَانَتْ مِثْلَ زَبَدِ الْبَحْرِ))
It is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, said: Whoever, after every prayer, says thirty-three times "Subhan Allah," thirty-three times "Alhamdulillah," and thirty-three times "Allahu Akbar," these become ninety-nine (words). Then, to complete one hundred (100), he says: "La ilaha illallahu wahdahu la sharika lahu, lahu’l-mulku wa lahu’l-hamdu wa huwa ‘ala kulli shay’in qadeer." His sins will be forgiven, even if they are as much as the foam of the sea.