Musnad Ahmad 962:144

Mu'awiyah ibn 'Amr narrated to us, Zaidah narrated to us, from 'Asim, from Shahr ibn Hawshab, from Abu Umamah, who said: If I had not heard it from the Prophet, may Allah bless him and grant him peace, at least seven times, I would not have narrated it. He said: "When a man performs wudu' as he was commanded, the sin departs from his hearing, his sight, his hands, and his feet."