Musannaf Ibn Abi Shayba 35:267

Ibn Fudayl narrated to us, from Layth, from ‘Abd al-Malik ibn Maysarah, from al-Nazzal ibn Sabrah, from ‘Ali, who said: "There is no divorce except after a marriage." And he mentioned that Abu Hanifah said: "If he swore by her divorce, then married her, she becomes divorced."