The Messenger of Allah ﷺ used to bathe from major ritual impurity with a saa of water, and perform ablution with a mudd.In another narration, the Messenger of Allah ﷺ used to bathe with a saa and purify himself with a mudd.
كان رسول الله ﷺ يغسله الصاع من الماء من الجنابة، ويوضئه المد. وفي رواية: كان رسول الله ﷺ يغتسل بالصاع، ويتطهر بالمد.
Muslim narrated it in "Menstruation" (326) through the route of Bishr bin Mufaddal, who said, "Abu Rayhana narrated to us, from Safinah." The second narration he related through the route of Ali bin Hajar, who said, "Ismail narrated to us, from Abu Rayhana, from him."Muslim said, "Abu Rayhana said, and he had grown old by then, and I did not trust his hadith" (meaning Safinah).Nawawi, may Allah have mercy on him, said, "Muslim, may Allah have mercy on him, did not mention this hadith of his relying on it alone, rather he mentioned it as corroboration alongside the other hadiths he mentioned." End of quote.As for Safinah, he was a companion of the Messenger of Allah ﷺ and his freed slave, and his name was Mihran bin Faruq, though other names have also been mentioned. It is said that the reason he was named Safinah is that he carried a great deal of baggage for a group of companions during a military expedition, so the Prophet ﷺ said to him, "You are a ship (Safinah)." Ahmad narrated this (21925) with a hasan chain of transmission.