Salim bin Abdullah (may Allah have mercy on him) said that Sayyiduna Abdullah bin Umar (may Allah be pleased with him) divorced his wife while she was menstruating. Sayyiduna Umar (may Allah be pleased with him) mentioned it to the Messenger of Allah (peace and blessings be upon him), and the Messenger of Allah (peace and blessings be upon him) became angry and said: "Let him take her back and keep her until she becomes pure, then wait for the purity after the next menstruation. If he intends to divorce her, let him divorce her in that purity before having intercourse. This is the period which Allah, the Lord of Might, has commanded."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14909