Chapter on Menstruation, Istihada (abnormal bleeding), and Nifas (postpartum bleeding)

Narrated from Amr ibn Uthman, from Al-Hasan ibn Mahbub, from Ali ibn Ri'ab, from Sama’ah: I asked Abu Abdillah عليه السلام about a woman in a state of istihadah (prolonged irregular bleeding). Imam عليه السلام said: "She must fast during the month of Ramadan, except for the days in which she used to have her menstrual period. She should then make up those days afterward."