Musnad Ahmad 1153:1363

Muhammad ibn Ja'far narrated to us, he said: Muhammad ibn 'Amr narrated to us, from Abu Salamah, from 'Aishah, she said: "I used to perform ghusl (ritual bath) with the Messenger of Allah, peace and blessings of Allah be upon him, from a single vessel due to janabah (major ritual impurity)."