He heard him say, "We used to sell our concubines and the mothers of our children while the Prophet ﷺ was alive among us, and he saw no harm in that."
حدثنا عبد الرزاق أخبرنا ابن جريج أخبرني أبو الزبير
أنه سمعه يقول إنا كنا نبيع سرارينا وأمهات أولادنا والنبي ﷺ فينا حي لا يرى بذلك بأسا
Its isnad is sahih. Some scholars held that it was abrogated, so the sale of a slave mother who has borne her master's child became forbidden. The hadith is found in Hakim, 2/18, where he graded it sahih and Dhahabi agreed with him. It is also found in Musnad Shafii, number 1205.