Abu Wa'il says that Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) divorced his wife while she was menstruating, so the Prophet (peace and blessings be upon him) ordered him to take her back: "until she becomes pure; when she becomes pure, then divorce her."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14925