Musannaf Ibn Abi Shayba 13:612

Abu Bakr narrated to us, he said: Ibn Sulayman narrated to us, from Salih ibn Hayy, from al-Sha’bi, who said: The prescribed punishment (hadd) of the owned slave is the prescribed punishment of the mukatab (slave under a contract of manumission), as long as there remains a dirham [of his debt] upon him.