Musannaf Ibn Abi Shayba 13:3066

Abu Bakr narrated to us, he said: Hushaym narrated to us, from Uthman al-Batti, from some of the companions of Ibrahim, regarding a man who gave permission to his slave, so he incurred debt, and the master died while he (the master) had debt. He said: The debt of the master is begun before the debt of the slave. Al-Batti said: I do not like that. The debt of the slave is begun before the debt of the master, because he has already pledged his neck.