حَدَّثَنِي مَالِكٌ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ أَيُّمَا وَلِيدَةٍ وَلَدَتْ مِنْ سَيِّدِهَا فَإِنَّهُ لاَ يَبِيعُهَا وَلاَ يَهَبُهَا وَلاَ يُوَرِّثُهَا وَهُوَ يَسْتَمْتِعُ بِهَا فَإِذَا مَاتَ فَهِيَ حُرَّةٌ ‏.‏

Malik related to me from Nafi from Abdullah ibn Umar that Umaribn al-Khattab said, "If a slave-girl gives birth to a child by hermaster, he must not sell her, give her away, or bequeath her. Heenjoys her and when he dies she is free ." Translation Not Available

Book reference: Muwatta Imam Malik Book 38 Hadith 1471
Web reference: Muwatta Imam Malik Book 38 Hadith 6