Sayyidah Salamah bint Ma'qil (may Allah be pleased with her) narrated: I was the slave-woman of Sayyiduna al-Hubab bin Amr (may Allah be pleased with him). He died, and I had a child by him. His wife said: Now you will be sold to pay off his debt. So I came to the Messenger of Allah (peace and blessings be upon him) and mentioned that to him. He (peace and blessings be upon him) said: "Who is responsible for the estate of al-Hubab?" His brother, Sayyiduna Abu al-Yasar Ka'b bin Amr (may Allah be pleased with him), said (that it was he). The Prophet (peace and blessings be upon him) called him and said: "Do not sell her; set her free. And whenever you hear that a slave has come to me, come to me and I will compensate you for her." So they did that. After the death of the Messenger of Allah (peace and blessings be upon him), they differed among themselves about this: some said: The umm walad (slave-mother of her master's child) remains a slave, otherwise the Prophet (peace and blessings be upon him) would not have compensated them. And some said: She is free; the Prophet (peace and blessings be upon him) had set her free.
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3583