Musnad Abu Ya'la al-Mawsili 148:88

Abu Bakr ibn Abi Shaybah narrated to us, Zayd ibn al-Hubab narrated to us, he said: al-Rabi’ ibn Sulaym narrated to me, he said: Abu ‘Amr, the freed slave of Anas ibn Malik, narrated to me that he heard Anas ibn Malik saying: The Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever guards his tongue, Allah will conceal his faults. Whoever restrains his anger, Allah will withhold His punishment from him. And whoever apologizes to Allah, Allah will accept his apology."