Yahya bin Sa'id heard Sa'id bin al-Musayyib (may Allah have mercy on him) say: "When a man makes his slave-girl mudabbarah, he may have intercourse (wati') with her, but he may not sell her or give her as a gift, and her children have her status."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المدبر / 21589