Jeremiah 34:8 (KJV)

Then Jeremiah the prophet spake all these words unto Zedekiah king of Judah in Jerusalem,

When the king of Babylon’s army fought against Jerusalem, and against all the cities of Judah that were left, against Lachish, and against Azekah: for these defenced cities remained of the cities of Judah.

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.

Now when all the princes, and all the people, which had entered into the covenant, heard that every one should let his manservant, and every one his maidservant, go free, that none should serve themselves of them any more, then they obeyed, and let them go.