Musannaf Ibn Abi Shayba 9:226

Ibn Idris narrated to us, from Malik, from al-Zuhri, that Abu Abd al-Rahman asked Zayd ibn Thabit about a slave woman who was under a man, and he divorced her irrevocably, then he bought her. He said: "She is not lawful for him except from where she became unlawful for him."