Musannaf Ibn Abi Shayba 13:660

Abu Bakr narrated to us, he said: Ma'n ibn 'Isa narrated to us, from Ibn Abi Dhi'b, from al-Zuhri, who said: The child of the *umm al-walad* (slave woman who has borne a child to her master) is in the same position as she is; they are emancipated by her emancipation, and they are enslaved by her enslavement.