Sunan An-Nasai, Chapter: The Book of Purification

that Umm Habibah bint Jahsh used to suffer from Istihadah (non-menstrual vaginal bleeding) for seven years. She asked the Prophet (saw) and he said: "That is not menstruation, rather it is a vein. Tell her not to pray for the amount of time that the period used to last, then let her perform Ghusl and pray." She used to perform Ghusl for every prayer. (Sahih)