Abu Zubair narrated that he heard Abdullah bin Ayman asking Ibn Umar (may Allah be pleased with them both), and Abu Zubair was listening: "What is your opinion about a man who divorces his wife while she is menstruating?" He replied that during the time of the Prophet ﷺ, Abdullah bin Umar (may Allah be pleased with them both) divorced his wife while she was menstruating. When Umar (may Allah be pleased with him) asked the Messenger of Allah ﷺ about this, the Messenger of Allah ﷺ said: "Tell Ibn Umar to take her back." She was returned to me and it was not considered a problem, and he said: "When she becomes pure from her menstruation, then if you wish, divorce her or keep her in marriage."
Hadith Referenceمسند الإمام الشافعي / كتاب الطلاق / 1242