Silsilat al-Ahadith al-Sahihah

Sayyiduna Khawwat bin Jubayr (may Allah be pleased with him) says: A man passed away, and among the wealth he had made me a trustee of, there was his umm walad (a slave woman who had borne him a child) and his free wife. A dispute arose between the umm walad and the wife. The wife said: "O lowly woman! One day, your ear will be grabbed and you will be sold in the market." The umm walad informed the Messenger of Allah (peace and blessings be upon him) of this. The Prophet (peace and blessings be upon him) said: "An umm walad is not to be sold."