Jeremiah 34:8-10

8This is the word that came to Jeremiah from the LORD, after king Zedekiah had made a covenant with all the people who were at Jerusalem, to proclaim liberty to them; 9That every man should release his male servant, and every man his female servant, being a Hebrew man or woman; that none should retain them in service, that is, a Jew his brother. 10Now when all the princes, and all the people, who had entered into the covenant, heard that every one should release his male servants, and every one his female servants, that none should retain them in service any more, then they obeyed, and let them go.