Jami` at-Tirmidhi 3468
Abu Hurairah narrates that:
The Mesenger of Allah (ﷺ) said: “Whoever says: ‘There is none worthy of worship except Allah, Alone, without partner, to Him belongs all that exists and to Him belongs the praise, He gives life and causes death, and He is Powerful over all things, (Lā ilāha illallāh, waḥdahu lā sharīka lahu, lahul-mulku wa lahul-ḥamdu, yuḥyī wa yumītu, wa huwa `alā kulli shay’in qadīr)’ a hundred times in a day, it will be for him the equivalent of freeing ten slaves, and there shall be written for him a hundred good deeds, and a hundred bad deeds shall be wiped out for him, and it will be a protection for him from Shaitan on that day, until he reaches the evening. And none has brought better than it, except for one who has done more than that.” And with this chain, from the Prophet (ﷺ), that he said: “Whoever says: ‘Glory is to Allah, and with His Praise (Subḥān Allāh, wa biḥamdih)’ a hundred times, his sins are forgiven, even if they were more than the foam of the sea.”
حَدَّثَنَا إِسْحَاقُ بْنُ مُوسَى الأَنْصَارِيُّ، حَدَّثَنَا مَعْنٌ، حَدَّثَنَا مَالِكٌ، 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 يُحْيِي وَيُمِيتُ وَهُوَ عَلَى كُلِّ شَيْءٍ قَدِيرٌ فِي يَوْمٍ مِائَةَ مَرَّةٍ كَانَتْ لَهُ عِدْلَ عَشْرِ رِقَابٍ وَكُتِبَتْ لَهُ مِائَةُ حَسَنَةٍ وَمُحِيَتْ عَنْهُ مِائَةُ سَيِّئَةٍ وَكَانَ لَهُ حِرْزًا مِنَ الشَّيْطَانِ يَوْمَهُ ذَلِكَ حَتَّى يُمْسِيَ وَلَمْ يَأْتِ أَحَدٌ بِأَفْضَلَ مِمَّا جَاءَ بِهِ إِلاَّ أَحَدٌ عَمِلَ أَكْثَرَ مِنْ ذَلِكَ ‏"‏ ‏.‏ 
وَبِهَذَا الإِسْنَادِ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏"‏ مَنْ قَالَ سُبْحَانَ اللَّهِ وَبِحَمْدِهِ مِائَةَ مَرَّةٍ حُطَّتْ خَطَايَاهُ وَإِنْ كَانَتْ أَكْثَرَ مِنْ زَبَدِ الْبَحْرِ ‏"‏ ‏.‏ قَالَ هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ.