Once, Sayyiduna Ibn Umar (may Allah be pleased with them both) divorced his wife while she was in her menstrual period. Sayyiduna Umar (may Allah be pleased with him) went and informed the Prophet (peace and blessings be upon him) about this. The Prophet (peace and blessings be upon him) said: "Tell him to take her back, then if he wishes to divorce her, he should do so during her period of purity."