Musannaf Ibn Abi Shayba 18:607

Abu Bakr narrated to us, he said: Yazid bin Harun narrated to us, from Muhammad bin Salim, from ‘Amir, who said: The crime (jinayah) of the mudabbar (a slave promised freedom upon the master's death) and the umm al-walad (a slave woman who has borne her master a child) is upon the ‘aqilah (the paternal relatives who pay blood money) of their masters.