Deuteronomy 19:17-21

19:17 then both parties to the controversy must stand before the Lord, that is, before the priests and judges who will be in office in those days. 19:18 The judges will thoroughly investigate the matter, and if the witness should prove to be false and to have given false testimony against the accused, 19:19 you must do to him what he had intended to do to the accused. In this way you will purge evil from among you. 19:20 The rest of the people will hear and become afraid to keep doing such evil among you. 19:21 You must not show pity; the principle will be a life for a life, an eye for an eye, a tooth for a tooth, a hand for a hand, and a foot for a foot.