Sayyidah Sallamah bint Ma'qil (may Allah be pleased with her) said: I was the slave woman of Hubab bin Amr (may Allah be pleased with him). He died, and I had a child from him. His wife said: "Now you will be sold to pay his debt." I mentioned this to the Messenger of Allah (peace and blessings be upon him), and the Messenger of Allah (peace and blessings be upon him) said: "Who is in charge of the estate of Hubab bin Amr?" They said: "His brother, Abu al-Yasar Ka'b bin Amr (may Allah be pleased with him)." The Messenger of Allah (peace and blessings be upon him) called him and said: "Set her free and do not sell her. When you hear that slaves have come to me, come to me and I will compensate you for her." They did so. After the death of the Messenger of Allah (peace and blessings be upon him) they differed among themselves. Some said: "The umm walad is a slave; had it not been so, the Messenger of Allah (peace and blessings be upon him) would not have compensated them for her." Others said: "She is free, because the Messenger of Allah (peace and blessings be upon him) had set her free."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21777