Musannaf Ibn Abi Shayba 1:706

Abu Bakr narrated to us, he said: Isma'il ibn 'Ulayyah narrated to us, from Abu Rayhanah, from Safinah, the companion of the Messenger of Allah (may Allah bless him and grant him peace), who said: The Messenger of Allah (may Allah bless him and grant him peace) used to perform ghusl with a sa' and perform wudu with a mudd.