It is narrated from Ibn Zayd al-Ansari (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) performed ablution with about two thirds of a mudd (of water).
Abu Zur'ah al-Razi said: In my view, the correct one is the hadith of Ghundar.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 943