Musannaf Ibn Abi Shayba 19:218

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Ali ibn Mubarak, from Yahya ibn Abi Kathir, from Ikrimah, from Ibn Abbas, who said: The prescribed punishment (hadd) for the mukatab (a slave under a contract of manumission) is the prescribed punishment for the slave, as long as anything remains of his contract of manumission.