Jeremiah 34:15-16

And ye were now turned, and had done that which is right in mine eyes, in proclaiming liberty every man to his neighbor; and ye had made a covenant before me in the house which is called by my name: but ye turned and profaned my name, and caused every man his servant, and every man his handmaid, whom ye had let go free at their pleasure, to return; and ye brought them into subjection, to be unto you for servants and for handmaids.