Nafi' (may Allah have mercy on him) mentioned a story in which Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) asked: "Do you know Sayyiduna Umar bin al-Khattab (may Allah be pleased with him)?" He said: "Yes." He said: He (Sayyiduna Umar (may Allah be pleased with him)) said: "Any slave woman who bears a child to her master, he may enjoy her during his lifetime, and when he dies she is free. Whoever has intercourse with a slave woman and then neglects her, the child is his and the loss is upon him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب عتق أمهات الأولاد / 21804