Muhammad bin Khazim al-Darir محمد بن خازم أبو معاوية الضرير · The Book of Menstruation and Istihadah

Fatimah bint Abi Hubaish came to the Messenger of Allah (ﷺ) and said: "I am a woman who suffers from Istihadah and I never become pure. Should I stop praying?" He said: "No, that is a vein, it is not menstruation. When your period comes, stop praying, and when it goes, wash the blood from yourself and pray."