Meaning of the Ten-Day Rule for a Woman with a Menstrual Habit - Jurisprudential Answers - Book of Purification

Ahmed al-Hasan Response:

It means that a woman with an established habit checks with cotton after her usual days have ended. If the cotton comes out clean, she performs ghusl. If it is stained, she waits until she becomes clean and then performs ghusl. If she does not become clean, or the bleeding continues for three days after the end of her usual period, she performs ghusl even if she has not become clean. If the bleeding continues to the tenth day and then stops, she makes up the fasting she performed because those were days of menstruation. If the bleeding exceeds ten days, what she performed is sufficient because those were days of istihada-that is, days of purity rather than days of menstruation.