كتاب الذكر والدعاء والتوبة والاستغفار
48
The Book Pertaining to the Remembrance of Allah, Supplication, Repentance and Seeking Forgiveness
(10)
Chapter: The Virtue Of Tahlil (Saying La Ilaha Ill-Allah), Tasbih (Saying Subhan Allah) And (Du'a) Supplication
(10)
باب فَضْلِ التَّهْلِيلِ وَالتَّسْبِيحِ وَالدُّعَاءِ

Abu Huraira reported Allah's Messenger (ﷺ) as saying:

He who uttered these words:" There is no god but Allah, the One, having no partner with Him. Sovereignty belongs to Him and all the praise is due to Him, and He is Potent over everything" one hundred times every day there is a reward of emancipating ten slaves for him, and there are recorded hundred virtues to his credit, and hundred vices are blotted out from his scroll, and that is a safeguard for him against the Satan on that day till evening and no one brings anything more excellent than this, except one who has done more than this (who utters these words more than one hundred times and does more good acts) and he who utters:" Hallowed be Allah, and all praise is due to Him," one hundred times a day, his sins are obliterated even if they are equal to the extent of the foam of the ocean.
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ سُمَىٍّ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ مَنْ قَالَ لاَ إِلَهَ إِلاَّ اللَّهُ وَحْدَهُ لاَ شَرِيكَ لَهُ لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ وَهُوَ عَلَى كُلِّ شَىْءٍ قَدِيرٌ ‏.‏ فِي يَوْمٍ مِائَةَ مَرَّةٍ ‏.‏ كَانَتْ لَهُ عَدْلَ عَشْرِ رِقَابٍ وَكُتِبَتْ لَهُ مِائَةُ حَسَنَةٍ وَمُحِيَتْ عَنْهُ مِائَةُ سَيِّئَةٍ وَكَانَتْ لَهُ حِرْزًا مِنَ الشَّيْطَانِ يَوْمَهُ ذَلِكَ حَتَّى يُمْسِيَ وَلَمْ يَأْتِ أَحَدٌ أَفْضَلَ مِمَّا جَاءَ بِهِ إِلاَّ أَحَدٌ عَمِلَ أَكْثَرَ مِنْ ذَلِكَ ‏.‏ وَمَنْ قَالَ سُبْحَانَ اللَّهِ وَبِحَمْدِهِ فِي يَوْمٍ مِائَةَ مَرَّةٍ حُطَّتْ خَطَايَاهُ وَلَوْ كَانَتْ مِثْلَ زَبَدِ الْبَحْرِ ‏"‏ ‏.‏
Reference : Sahih Muslim 2691
In-book reference : Book 48, Hadith 38
USC-MSA web (English) reference : Book 35, Hadith 6508
  (deprecated numbering scheme)