Musannaf Ibn Abi Shayba 9:1553

Abu Bakr narrated to us, he said: Sufyan ibn ‘Uyaynah narrated to us, from ‘Ubayd Allah ibn Abi Yazid, that he asked Ibn ‘Abbas about a man who bought a slave woman while she was pregnant: "May he have intercourse with her?" He said: "No." And he recited: "And for those who are pregnant, their term is until they give birth."