The Messenger of Allah ﷺ used to bathe with a saa of water and perform ablution with a mudd.
حدثنا أحمد بن محمد بن حنبل حدثنا هشيم أخبرنا يزيد بن أبي زياد عن سالم بن أبي الجعد
كان رسول الله ﷺ يغتسل بالصاع ويتوضأ بالمد
[Sahih]. Ahmad reported it: 3/303, from Hushaym, with the same wording, and Ibn Khuzayma graded it sahih, no. 117.Husayn also narrated it from Salim bin Abu Jaad, as found in Bayhaqi: 1/195, and Hakim: 1/161.The hadith has many corroborating narrations, including the previous hadith.