Musnad Ahmad 1153:1841

Hajjaj narrated to us, he said: Layth narrated to us, from Yazid ibn Abi Habib, from Ja'far ibn Rabi'ah, from 'Arak, from 'Urwah, from 'Aishah, she said: Umm Habibah asked the Messenger of Allah, peace and blessings of Allah be upon him, about the blood. 'Aishah said: I saw her basin full of blood. The Messenger of Allah, peace and blessings of Allah be upon him, said to her: "Wait for the duration that your menstruation used to hold you back, then perform ghusl and pray."