Excluded by his statement, “during a period of purity,” is the case in which he divorces her while she is menstruating or in postnatal bleeding; this is not a Sunnah-compliant divorce. Its explanation will come, Allah willing.
His statement, “during a period of purity in which he has not had intercourse with her,” excludes the case in which he divorces her during a period of purity in which he did have intercourse with her. Such a divorce is an innovated divorce, even if that period of purity has lasted a long time. For example, suppose that this man’s wife becomes pure from postnatal bleeding, and he has intercourse with her while she is breastfeeding. Usually, a breastfeeding woman does not menstruate until she weans the child—that is, after approximately two years. Thus, if he divorces her at any point during those two years, it is an innovated divorce, because it occurred during a period of purity in which he had intercourse with her. He must therefore wait until she menstruates and then becomes pure.
His statement, “and leaves her until her waiting period expires,” means that if he follows it with another pronouncement of divorce, it is an innovated divorce. For example, if he says, “You are divorced,” and she begins her waiting period, then two, three, or ten days later he says, “You are divorced,” we say: this divorce is innovated and not Sunnah-compliant. The evidence is the saying of Allah, Most High: “O Prophet, when you divorce women, divorce them at the commencement of their waiting period” [al-Talaq 65:1]. The Prophet, peace and blessings be upon him, explained the waiting period as divorcing her during a period of purity in which he has not had intercourse with her (1).
His statement, “during a period of purity,” indicates that this woman is one who menstruates. As for one who does not menstruate, it is permissible to divorce her even during a period of purity in which he has had intercourse with her, since there is no period of purity or menstruation in her case. From the moment he divorces her, she begins her waiting period, for her waiting period is reckoned in months.