Muwatta Malik, Book 15, Hadith 21 (USC-MSA) ⓘ

Yahya related to me from Malik from Sumayy, the mawla of Abu Bakr, from Abu Salih as-Samman from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, "Whoever says, 'Glory be to Allah and with His praise' (Subhana'llah wa bi-hamdihi) one hundred times in a day will have his wrong actions taken away from him, even if they are as abundant as the foam on the sea."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ سُمَىٍّ، مَوْلَى أَبِي بَكْرٍ عَنْ أَبِي صَالِحٍ السَّمَّانِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ مَنْ قَالَ سُبْحَانَ اللَّهِ وَبِحَمْدِهِ فِي يَوْمٍ مِائَةَ مَرَّةٍ حُطَّتْ عَنْهُ خَطَايَاهُ وَإِنْ كَانَتْ مِثْلَ زَبَدِ الْبَحْرِ ‏" ‏ ‏.‏