Musannaf Ibn Abi Shayba 13:664

Abu Bakr narrated to us, he said: Ibn Abi Za’idah and Ibn al-Musayyib narrated to us, from Ubaydullah, from Nafi’, from Ibn Umar, he said: The child of a freedwoman (born) from a condition of *dabr* (post-death emancipation) follows her status; they are enslaved by her enslavement and freed by her emancipation.