It is narrated from Ibn Umar (may Allah be pleased with them both) that he divorced his wife during her menstruation in the time of the Prophet ﷺ. When Umar (may Allah be pleased with him) asked the Messenger of Allah ﷺ about this, the Messenger of Allah ﷺ said: "Order Ibn Umar to take her back." The Prophet ﷺ returned the woman to me without any objection, and said: "When she becomes pure from her menstruation, then he may divorce her or keep her in his marriage."
Hadith Referenceمسند الإمام الشافعي / كتاب الطلاق / 1243