Nafi' (may Allah have mercy on him) narrates from Abdullah bin Umar (may Allah be pleased with them both) that a man should not have intercourse with a slave-woman except a slave-woman whom, if he wishes, he may sell, if he wishes, he may gift, and if he wishes, he may do with her whatever he wants.
The Shaykh (may Allah have mercy on him) says: In his new view, Imam al-Shafi'i (may Allah have mercy on him) forbade a slave from taking a slave-woman, and he countered the first report with this one; yet Ibn Umar (may Allah be pleased with them both) said this only about a free man who buys a slave-woman with an invalid condition.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13854