Musannaf Ibn Abi Shayba 9:963

Yazid ibn Harun narrated to us, from al-Jurayri, who said: I asked Ghunaym ibn Qays. I said: "Does the slave marry without the permission of his master? Is it adultery?" He said: "He has disobeyed." I said: "Is it adultery?" He said: "He has disobeyed."