Maliks Muwatta Book 2, Hadith Number 30.
Yahya related to me from Malik from Hisham ibn Urwa from his father from Humran, the mawla of Uthman ibn Affan, that Uthman ibn Affan was once sitting on the Maqaid (the benches surrounding the Madina Mosque, or else a stone near Uthman ibn Affan’s house where he sat to discuss with people), when the muadhdhin came and told him that it was time for the asr prayer. He called for water and did wudu. Then he said, “By Allah, I shall tell you something which I would not tell you if it were not in the Book of Allah. I heard the Messenger of Allah, may Allah bless him and grant him peace, say, ‘If a man does wudu, and makes sure he does it correctly, and then does the prayer, he will be forgiven everything that he does between then and the time when he prays the next prayer.'”
Yahya said that Malik said, “I believe he meant this ayat – ‘Establish prayer at the two ends of the day and in some watches of the night. Good actions take away wrong actions. That is a reminder for those who remember.'” (Sura 11 ayat 114).