'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. (ID)
English reference (ID): Vol. 1, Book 1, Hadith 270 (ID)
Arabic reference (ID): Book 1, Hadith 282 (ID)