Deuteronomy 19:15-21 New King James Version (NKJV)
The Law Concerning Witnesses
15 “One witness shall not rise against a man concerning any iniquity or any sin that he commits; by the mouth of two or three witnesses the matter shall be established. 16 If a false witness rises against any man to testify against him of wrongdoing, 17 then both men in the controversy shall stand before the Lord, before the priests and the judges who serve in those days. 18 And the judges shall make careful inquiry, and indeed, if the witness is a false witness, who has testified falsely against his brother, 19 then you shall do to him as he thought to have done to his brother; so you shall put away the evil from among you. 20 And those who remain shall hear and fear, and hereafter they shall not again commit such evil among you. 21 Your eye shall not pity: life shall be for life, eye for eye, tooth for tooth, hand for hand, foot for foot.