Musnad Ahmad 3:105

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Jami' ibn Shaddad, he said: I heard Humran ibn Aban narrating to Abu Burdah in the mosque that he heard Uthman ibn Affan narrating from the Prophet, may Allah bless him and grant him peace, that he said: "Whoever performs the ablution completely as Allah has commanded him, then the prescribed prayers are expiations for what is between them."