Musnad Abu Ya'la al-Mawsili 149:49

Al-Hakam ibn Musa narrated to us, Hagl narrated to us, from al-Awza'i, who said: al-Zuhri narrated to me, 'Urwah ibn al-Zubayr narrated to me, from 'Amrah bint 'Abd al-Rahman ibn Sa'd ibn Zurarah, from 'Aishah, who said: Umm Habibah bint Jahsh—who was under the marriage of 'Abd al-Rahman ibn 'Awf—experienced *istihada* (prolonged non-menstrual bleeding) for seven years. She complained of that to the Messenger of Allah, and the Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, this is not menstruation; it is only a vein. So when the menstruation arrives, abandon the prayer, and when it departs, perform ghusl (ritual bath), then pray." 'Aishah said: She used to perform ghusl for every prayer, and she would sit in a washbasin for her sister, Zaynab bint Jahsh, until the redness of the blood would appear on the water.