Sahih al-Bukhari 6403
صحيح البخاري#6403SahihNarrated Abu Huraira: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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 80:98