Sunan an-Nasa'i, Volume 1, Book 1, Hadith 227 (DarusSalam)

It was narrated that Musa Al-Juhani said: "A vessel was brought to Mujahid, which I estimated to be eight Ratls, and he said: 'Aishah told me that the Messenger of Allah used to perform Ghusl using such a vessel.'"

أَخْبَرَنَا مُحَمَّدُ بْنُ عُبَيْدٍ، قَالَ حَدَّثَنَا يَحْيَى بْنُ زَكَرِيَّا بْنِ أَبِي زَائِدَةَ، عَنْ مُوسَى الْجُهَنِيِّ، قَالَ أُتِيَ مُجَاهِدٌ بِقَدَحٍ حَزَرْتُهُ ثَمَانِيَةَ أَرْطَالٍ فَقَالَ حَدَّثَتْنِي عَائِشَةُ رضى الله عنها أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَغْتَسِلُ بِمِثْلِ هَذَا ‏.‏

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also referenced under: Book 1, Hadith 228 (In-Book)