Sayyiduna Anas (may Allah be pleased with him) narrates: I remember that we used to buy and sell umm walad slave women while the Prophet (peace and blessings be upon him) was present among us.
Al-Bazzar recorded it; its chain contains a narrator Mu'awiyah bin Yahya al-Sadafi, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب البيوع / 6521