It is narrated from Al-Husayn ibn Sa’id, from Uthman ibn Isa, from Sa’id ibn Yasar, who said: I asked Abu Abdullah عليه السلام about a woman who menstruates and then becomes pure but sometimes sees a small amount of thin blood after performing ghusl for her purification. Imam عليه السلام said: "She should wait for one, two, or three days as a precaution after her regular menstrual days, and then she should pray."