Jeremiah 34:8-9

The word that came unto Jeremiah from Jehovah, after that the king Zedekiah had made a covenant with all the people that were at Jerusalem, to proclaim liberty unto them; that every man should let his man-servant, and every man his maid-servant, that is a Hebrew or a Hebrewess, go free; that none should make bondmen of them, to wit, of a Jew his brother.