Musannaf Ibn Abi Shayba 9:215

Hammad ibn Khalid narrated to us, from Ibn Abi Dhi'b, who said: I asked 'Ata' about a man who has a slave woman under him [as a wife], then he buys her. He said: "She is a slave woman; he may do with her whatever he wishes." He said: And I asked al-Zuhri, and he said the same as that.