Musannaf Ibn Abi Shayba 19:478

Abu Bakr narrated to us, he said: Yahya ibn Sa'id al-Qattan narrated to us, from Sufyan, from al-Shaybani, from al-Sha'bi, from 'Amir ibn Matar, from 'Abdullah, regarding a man who has intercourse with his wife's slave girl: He said: If he forced her, then she is free, and he owes her equivalent to her master. And if she obeyed him, then she is his, and he owes her equivalent to her mistress.