Musnad Ahmad 28:527

'Affan narrated to us, Hammad ibn Salamah narrated to us, from Thabit and Dawud ibn Abi Hind, from 'Amr ibn Shu'ayb, from his father, from his grandfather, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever says in a day two hundred times: 'There is no god but Allah alone, He has no partner, to Him belongs the dominion, and to Him belongs the praise, and He is capable of all things,' no one who was before him will surpass him, and no one who comes after him will overtake him, except for one who does better than his deed." Meaning: Except for one who does a deed better than his deed.