Musnad Abu Ya'la al-Mawsili 117:23

Ibrahim ibn al-Hajjaj al-Sami narrated to us, Bashar ibn al-Hakam narrated to us, Thabit al-Bunani narrated to us, from Anas, from the Prophet, peace be upon him, who said: "Indeed, a righteous trait exists in a man, and through it, Allah rectifies all of his deeds. And the purification of a man for his prayer—Allah expiates his sins through his purification, and his prayer remains for him as a supererogatory act."