It is narrated from Sayyidah Umm Umarah (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) performed ablution, and a vessel was brought to him (peace and blessings be upon him) containing water about two thirds of a mudd.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 941