Musnad Ahmad 3:75

Hashim narrated to us, Shu'bah narrated to us, he said: Abu Sakhr Jami' ibn Shaddad informed me, he said: I heard Humran ibn Aban narrating to Abu Burdah in the mosque of Basra, and I was standing with him, that he heard Uthman ibn Affan narrating from the Prophet, may Allah bless him and grant him peace, that he said: "Whoever performs wudu perfectly as Allah, the Almighty and Majestic, has commanded him, then the five prayers are expiations for what is between them."