Musannaf Ibn Abi Shayba 18:615

Abu Bakr narrated to us, he said: Jarir narrated to us, from Mughira, from his companions or from Ibrahim, he said: Whatever the *mukātab* (a slave who has entered into a contract of manumission) commits of a crime, it is upon his own neck; he pays for his crime and his manumission contract together.