Yahya related to me from Malik from Sumayy, the mawla of Abu
Bakr, from Abu Salih as-Samman from Abu Hurayra that the Messenger of
Allah, may Allah bless him and grant him peace, said, "Whoever says
'There is no god but Allah, alone, without any partner. The Kingdom
and praise belong to Him and He has power over everything' (La ilaha
illa'llah, wahdahu la sharika lah, lahu'l mulku wa lahu'l hamd, wa
huwa ala kulli shay'in qadir) one hundred times a day, it is the same
for him as freeing ten slaves. One hundred good actions are written
for him and one hundred wrong actions are erased from him, and it is a
protection from Shaytan for that day until the night. No-one does
anything more excellent than what he does except someone who does more
than that."
Muwatta Malik Book 15, Hadith 22