Sunan Ibn Majah

Abdullah bin Muhammed bin 'Aqil bin Abu Talib narrated from his father that his grandfather said:""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