Wabarah narrates from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both): When a man gives his wife one or two divorces, then another man marries that woman, then the first husband marries her again, he is entitled to three divorces anew.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 15141