Musannaf Ibn Abi Shayba 13:2865

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, from Mansur, from Ibrahim: That he sold the daughter of a slave-girl of his. Mansur said: So I said to him, "Did they not use to dislike separating [them]?" He said: "Yes, but her mother consented, and I have placed her in a good position."