Muhammad bin Suqah محمد بن سوقة · The Book of Purification and its Sunnah

"The Messenger of Allah said: 'A Mudd is sufficient for the ablution and a Sa' is sufficient for the bath.' A man said: 'It is not sufficient for us.'" He (the narrator) said: "It was sufficient for one who is better than you and had more hair" meaning the Prophet.