Musannaf Ibn Abi Shayba 1:1345

Waki' narrated to us, he said: Al-A'mash narrated to us, from Habib ibn Abi Thabit, from 'Urwah, from 'Aishah, she said: Fatima bint Abi Hubaysh came to the Prophet, may Allah bless him and grant him peace, and said: "O Messenger of Allah, I am a woman who experiences *istihada* (prolonged non-menstrual bleeding), so I do not become pure. Should I abandon the prayer?" He said: "No, that is only a vein, and it is not the menstruation. Refrain from prayer during the days of your menstruation, then perform *ghusl* (full ablution), and perform *wudu* (ablution) for every prayer, then pray, even if the blood drips onto the mat."