It is narrated from Abu Ubaydah that Sayyiduna Uthman (may Allah be pleased with him) sent a messenger to my father (Sayyiduna Abdullah bin Mas'ud, may Allah be pleased with him) to ask him about a man who divorced his wife and then took her back when she had entered her third menstruation. He said: My view is that he is more entitled to her as long as she has not taken the bath from her third menstruation and prayer has not become lawful for her. Abu Ubaydah said: I do not know Uthman (may Allah be pleased with him) to have done anything other than adopt that view.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العدد / 15396