Musannaf Ibn Abi Shayba 1:369

Ibn ‘Uyaynah narrated to us, from al-Zuhri, from ‘Urwah, from ‘A’ishah, who said: The Prophet (peace and blessings of Allah be upon him) used to perform ghusl from a *faraq*, and it is the *qadah* (vessel). And I and he used to perform ghusl from a single vessel.