It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: Whoever recites these words a hundred times during the day: "La ilaha illallah wahdahu la sharika lahu, lahul mulk wa lahul hamd wa huwa 'ala kulli shay'in qadeer," it will be equal to freeing ten slaves, and a hundred good deeds will be written for him, and a hundred sins will be erased, and it will be a means of protection from Satan for him until the evening. And no one will be able to present a deed superior to this except the one who does more than this.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 8008