Abdullah bin Dinar related from Sayyiduna Abdullah bin Umar (may Allah be pleased with him) that he divorced his wife while she was menstruating. Sayyiduna Umar (may Allah be pleased with him) informed the Messenger of Allah (peace and blessings be upon him), and the Messenger of Allah (peace and blessings be upon him) said: "Let him take her back until she becomes pure, then becomes pure from another menstruation; then after that let him divorce or keep her."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14914