to a woman who is menstruating, 'When you become pure, you are divorced,' she is divorced at the first instance of purity, and she is divorced in both cases upon the cessation of the menstrual blood before [performing] the ritual bath (ghusl). Ahmad stipulated this in a narration by Ibrahim al-Harbi. Abu Bakr mentioned in 'al-Tanbih' an opinion regarding this, that she is not divorced until she performs the ritual bath, based on the principle that the waiting period (idda) does not expire with the cessation of blood until she performs the ritual bath. To us, Allah Almighty said: {And do not approach them until they are pure} (10), meaning: their blood has ceased, {And when they have purified themselves} (10), meaning: they have performed the ritual bath. Furthermore, the rulings of pure women have been established for her regarding the obligation of prayer and the validity of purification and fasting, and only some rulings remain suspended upon the performance of the ritual bath. Moreover, she is not menstruating, so she must be pure; for they are two opposites defined by exclusion, so the existence of the one necessitates the absence of the other.

Chapter: If he says to her, 'When you menstruate one menstruation, you are divorced, and when you menstruate two menstruations, you are divorced.' If she menstruates one menstruation, she is divorced once. Then, when she menstruates the second, she is divorced the second time upon her purity from it. If he says, 'When you menstruate one menstruation, you are divorced, then when you menstruate two menstruations, you are divorced,' the second [divorce] does not take place until she becomes pure from the third menstruation; because 'then' (thumma) denotes sequence, so it requires two menstruations after the first divorce, as they are sequenced upon it.

Chapter: If he says, 'When you menstruate half a menstruation, you are divorced,' she is divorced when half of the menstruation has passed. It should be judged that the divorce has occurred when she has menstruated half of her [usual] habit; because the rulings were attached to the habit, so the occurrence of the divorce is attached to it. It is possible that it is not judged that the divorce has occurred until seven and a half days have passed; because we cannot be certain of the passage of half the menstruation except by that, unless she becomes pure in less time than that, and whenever she becomes pure, we establish that the divorce occurred at half of the menstruation. It is also said: his statement 'half a menstruation' is void, and her divorce remains suspended upon the existence of menstruation. The first [view] is more correct; for