Musannaf Ibn Abi Shayba 9:1183

Abu Dawud narrated to us, from Habib, from ‘Amr, from Jabir ibn Zayd, regarding a man who married a woman to make her lawful for her [previous] husband, while he [the previous husband] did not know. He said: The ruling is that he keeps her. And Hammad said: It is more beloved to me that he separates from her.