It is narrated from Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) that if a man divorces his wife, he has more right to take her back until the woman performs ghusl after her third menstruation. This ruling is after the first and second divorce.
Hadith Referenceالسنن المأثورة / باب تفسير الفرعة والعتيرة / 412
Hadith Takhrijالسنن الكبرى للبيهقي: 471/7 و مصنف عبدالرزاق: 315/6، سنن سعید بن منصور: 290/1 ۔