Musnad Ahmad 1153:1077

Yazid narrated to us, he said: Ibn Abi Dhi'b informed us, from al-Zuhri, from 'Urwah and 'Amrah bint 'Abd al-Rahman, from 'Aishah: That Umm Habibah bint Jahsh experienced prolonged bleeding (istihadah) for seven years, and she was the wife of 'Abd al-Rahman ibn 'Awf. She asked the Messenger of Allah, peace and blessings of Allah be upon him, about that. The Messenger of Allah, peace and blessings of Allah be upon him, said: "This is only a vein, and it is not menstruation, so perform ghusl and pray." He said: So she used to perform ghusl for every prayer.