Musannaf Ibn Abi Shayba 3:5271

Waki’ narrated to us, [who] narrated from Mis’ar, from Abu Sakhra Jami’ ibn Shaddad, who said: I heard Humran ibn Aban, the freed slave of Uthman, saying: I used to place the water for Uthman’s purification, and not a day passed by him but that he would pour a drop of water from it upon himself. Uthman said: The Messenger of Allah (may Allah bless him and grant him peace) spoke to us when we had finished this prayer of ours—Mis’ar said: I think he said: "The Asr [afternoon] prayer"—and he said: "I do not know whether I should tell you or remain silent." We said: "O Messenger of Allah, if it is good, then tell us, and if it is otherwise, then Allah and His Messenger know best." The Messenger of Allah (may Allah bless him and grant him peace) said: "There is no man who performs ablution and perfects the ablution, then prays, but that he is forgiven for what is between it and the other prayer."