Deuteronomy 19:15-21 - Laws Concerning Witnesses
15 One witness shall not be valid against a man for any iniquity or for any sin, in any sin which he should commit. At the mouth of two witnesses or at the mouth of three witnesses, shall the matter be established.
16 When a false witness rises up against any man to testify rebellion against him, 17 then both the men, between whom the controversy is, shall stand before the LORD, before the priests and the judges, who shall be in those days; 18 and the judges shall make diligent inquisition; and, behold, if the witness is a false witness and has testified falsely against his brother, 19 then shall ye do unto him as he had thought to have done unto his brother; so shalt thou put the evil away from among you. 20 And those who remain shall hear and fear and shall never again commit any such evil among you. 21 And thine eye shall not pity, but life shall go for life, eye for eye, tooth for tooth, hand for hand, foot for foot.