The Prophet ﷺ used to bathe with a saa up to five mudds of water, and perform ablution with a single mudd.In another wording, he used to bathe with five makkuks and perform ablution with one makkuk.
كان النبي ﷺ يغتسل بالصاع إلى خمسة أمداد، ويتوضأ بالمد. وفي لفظ: كان يغتسل بخمس مكاكيك، ويتوضأ بمكوك.
Bukhari narrated it in the Book of Wudu (201) and Muslim in the Book of Menstruation (325), both through Masaar, who said, "Abdullah bin Abdullah bin Jabr told me, he said, I heard Anas..." and he related it. The second narration was reported by Muslim through Shuba, from Ibn Jabr.Makakik is the plural of makkuk (formed like the word tannur), and it is a unit of measure. Nawawi said, "Perhaps what is meant by makkuk here is the mudd, as stated in another narration, 'He would perform wudu with a mudd and perform ghusl with a saa up to five amdad.'" End of quote. And in the Sunan, "He would perform wudu with a vessel that held two ratls, and perform ghusl with a saa."Abu Dawud said in his Sunan (95), I heard Ahmad bin Hanbal say, "The saa is five ratls, and it is the saa of Ibn Abu Dhib, and it is the saa of the Prophet ﷺ."As for what is narrated from Anas bin Malik, who said, "I heard the Messenger of Allah ﷺ say, 'A mudd suffices for wudu, and a saa suffices for ghusl,'" this is an error. Abu Awana (629) narrated it from Hasan bin Ali bin Affan, who said, "Muawiya bin Hisham narrated to us, who said, Sufyan (that is, Thawri) narrated to us, from Abdullah bin Jabr, who said, I heard Anas bin Malik say," and he related it.Muawiya bin Hisham is Qassar. Imam Ahmad said of him that he makes many errors, and Ibn Adi said, "He has related unusual things from Thawri, and I hope he is not seriously flawed."I say, This is among his narrations from Thawri, in which he was unusual and erred, making the hadith a saying of the Messenger of Allah ﷺ, whereas the correct view is that it was his action ﷺ, as in the other hadiths.