It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that he divorced his wife while she was in her menstrual period. Sayyiduna Umar (may Allah be pleased with him) asked the Prophet Muhammad (peace and blessings be upon him) about this issue, so the Prophet Muhammad (peace and blessings be upon him) said: "Tell him to take his wife back, then after she becomes pure, he may divorce her, or if she is pregnant, he may also divorce her."