Musannaf Ibn Abi Shayba 19:927

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Sufyan, from Yahya ibn Sa’id, from ‘Umar ibn ‘Abd al-‘Aziz: That a *umm walad* (a slave woman who has borne a child to her master) of a man from the Muslims apostatized, so he sold her in Dumat al-Jandal to someone other than her people.