"The Messenger of Allah ﷺ said: 'Whoever says the tasbih one hundred times following the morning prayer, and the tahlil one hundred times, he will be forgiven his sins even if they are like the foam of the sea.'" (Using translation from Nasāʾī 1354)
أَنَّهُ قَالَ قَالَ رَسُولُ اللهِ ﷺ «مَنْ سَبَّحَ فِي دُبُرِ صَلَاةِ الْغَدَاةِ مِائَةَ تَسْبِيحَةٍ وَهَلَّلَ مِائَةَ تَهْلِيلَةٍ غُفِرَ لَهُ ذُنُوبَهُ وَلَوْ كَانَتْ مِثْلَ زَبَدِ الْبَحْرِ»