Anas bin Sirin said: A woman from the family of Anas was afflicted with the illness of istihada (non-menstrual bleeding), so they instructed me to ask the ruling from Sayyiduna Ibn Abbas (may Allah be pleased with them). He replied that when she sees a lot of red blood, she should not pray, and when she sees purity at any time during the day, she should perform ghusl and pray. (That is, even if the menstruation stops for a short while, she should perform ghusl and pray.)