If a woman's menstrual bleeding stops for an hour or more, then the blood or discolored discharge returns, should she perform ghusl and pray as soon as the temporary cessation occurs, or should she wait for complete dryness or the white discharge?

A woman observes purity by one of two signs: dryness (al-jufūf) or the white discharge (al-qaṣṣah al-bayḍā’). If she attains purity by dryness, meaning the cotton swab comes out clean, then the preponderant opinion is that she should promptly perform ghusl (ritual bath). If blood, yellowish discharge (ṣufrah), or brownish discharge (kudrah) reappears during her usual period, she reverts to being in a state of menstruation. This is the more cautious approach, acting upon the statement of Ibn ‘Abbās (may Allah be pleased with them both): “It is not permissible for her, once she sees purity for even an hour, not to perform ghusl.” There is another opinion which suggests that she may wait for a day and a half to ensure the cessation of blood flow.