Jeremiah 34:8-9

This is the word that came unto Jeremiah from the LORD, after that the king Zedekiah had made a covenant with all the people which were at Jerusalem, to proclaim liberty unto them; that every man should let his manservant, and every man his maidservant, being an Hebrew or an Hebrewess, go free; that none should serve himself of them, to wit, of a Jew his brother.