Musnad Abu Ya'la al-Mawsili 118:76

Hudhayl ibn Ibrahim al-Jumani narrated to us, Uthman ibn Abd al-Rahman al-Zuhri—from the descendants of Sa'd ibn Abi Waqqas—narrated to us, from al-Zuhri, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "No servant says 'There is no god but Allah' at any hour of the night or day, except that it erases what is in his scroll of bad deeds, until it settles with the like of it in good deeds."