The Prophet ﷺ used to bathe with a saa of water and perform ablution with a mudd.
حدثنا محمد بن كثير حدثنا همام عن قتادة عن صفية بنت شيبة
أن النبي ﷺ كان يغتسل بالصاع ويتوضأ بالمد
[Sahih] Ibn Majah reported it in Kitab Taharah, Bab Ma Jaa fi Miqdar al-Maa lil-Wudu wal-Ghusl min al-Janaba, no. 268, from the hadith of Hammam through this route, and Nasai also narrated it, no. 347. The hadith of Abu Aban bin Yazid Attar was reported by Bayhaqi, 1/195, and its chain of transmission is sahih.