(64) باب فَضْلِ التَّهْلِيلِ
Narrated 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."
Reference: Sahih al-Bukhari 6403
In-book reference: Book 80, Hadith 98
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 8, Book 75, Hadith 412