Sahih al-Bukhari 6403

أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ مَنْ قَالَ لاَ إِلَهَ إِلاَّ اللَّهُ، وَحْدَهُ لاَ شَرِيكَ لَهُ، لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ، وَهْوَ عَلَى كُلِّ شَىْءٍ قَدِيرٌ‏.‏ فِي يَوْمٍ مِائَةَ مَرَّةٍ، كَانَتْ لَهُ عَدْلَ عَشْرِ رِقَابٍ، وَكُتِبَ لَهُ مِائَةُ حَسَنَةٍ، وَمُحِيَتْ عَنْهُ مِائَةُ سَيِّئَةٍ، وَكَانَتْ لَهُ حِرْزًا مِنَ الشَّيْطَانِ يَوْمَهُ ذَلِكَ، حَتَّى يُمْسِيَ، وَلَمْ يَأْتِ أَحَدٌ بِأَفْضَلَ مِمَّا جَاءَ بِهِ إِلاَّ رَجُلٌ عَمِلَ أَكْثَرَ مِنْهُ ‏"‏‏.

“Allah's Messenger ﷺ said," Whoever says: "La ilaha illal-lah wahdahu la sharika lahu, lahu-l-mulk wa lahul- hamd wa huwa 'ala kulli shai'in qadir," one hundred times will get the same reward as given for manumitting ten slaves; and one hundred good deeds will be written in his accounts, and one hundred sins will be deducted from his accounts, and it (his saying) will be a shield for him from Satan on that day till night, and nobody will be able to do a better deed except the one who does more than he”