Ibn Abi al-Zinad (may Allah have mercy on him) narrates from his father (may Allah have mercy on him), and he from the jurists of Madinah, that whoever makes zihar from his wife and then divorces her before offering the expiation, and after that marries her again, should not go near his wife until he has offered the expiation.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الظهار / 15265