Does a man's divorce of his wife, whom he has not consummated the marriage with, take effect if he divorces her while she is menstruating?

The khul' (divorce initiated by the wife) that occurs during menstruation is valid, and you are not required to issue a second divorce. This is because khul' during menstruation is not prohibited according to most scholars. It is effective regardless of whether it is prohibited or not. Many scholars have held that khul' is permissible during menstruation because it is not a divorce but rather an irrevocable separation, and it is not an innovation (bid'ah). Sheikh al-Islam Ibn Taymiyyah held that khul' is a dissolution of the marriage in all cases, even if it occurs with the لفظ (wording) of divorce, because it is a ransom paid by the wife to her husband, and the consideration is for the meaning, not the wording.