Musnad Ahmad

It is narrated from Hazrat Umm Habibah (may Allah be pleased with her) that once she presented herself before the Prophet (peace and blessings be upon him) and complained about continuous menstrual bleeding. The Prophet (peace and blessings be upon him) instructed her to perform ghusl at the time of every prayer. Thus, when she would come out of the tub, the water would have become predominantly red, yet she would perform the prayer. He said to her, "This is blood from a vein, so observe: when the time of your menstrual period comes, do not perform the prayer, and when that period passes, consider yourself pure, perform purification, and continue to pray until the next period."

It is narrated from Hazrat Umm Habibah (may Allah be pleased with her) that once she came to the service of the Prophet (peace and blessings be upon him) and complained about the continuous flow of menstrual blood. The Prophet (peace and blessings be upon him) said to her: "This is not menstruation, it is blood from a vein, so you should perform ghusl (ritual bath)." Thus, she used to perform ghusl at the time of every prayer, and when she would come out of the tub, we would see the color of the water as red.