Musnad Ahmad 30:1752

Ishaq ibn Isa narrated to us, Malik informed me, from Sumayy, from Abu Salih, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever says: 'There is no god but Allah, alone, with no partner, to Him belongs the dominion, and to Him belongs the praise, and He is capable of all things' (La ilaha illallah, wahdahu la sharika lah, lahul-mulku wa lahul-hamdu, wa huwa 'ala kulli shay'in qadir) one hundred times in a day, it will be for him the equivalent of freeing ten slaves, and one hundred good deeds will be recorded for him, and one hundred evil deeds will be erased from him, and it will be a protection for him from Satan for that day until evening, and no one will bring anything better than what he has brought, except a man who does more than that. And whoever says in a day: 'Glory be to Allah and by His praise' (Subhanallahi wa bihamdihi) one hundred times, his sins will be removed, even if they were like the foam of the sea."