One witness shall not rise up against a man for any iniquity, or for any sin, in any sin that he sinneth: at the mouth of two witnesses, or at the mouth of three witnesses, shall the matter be established.
If a false witness rise up against any man to testify against him that which is wrong; then both the men, between whom the controversy is, shall stand before the LORD, before the priests and the judges, which shall be in those days; and the judges shall make diligent inquisition: and, behold, if the witness be a false witness, and hath testified falsely against his brother; 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.
And those which remain shall hear, and fear, and shall henceforth commit no more any such evil among you.  And thine eye shall not pity; but life shall go for life, eye for eye, tooth for tooth, hand for hand, foot for foot.  Deuteronomy 19:15-21

References: Deuteronomy 19:1-14; Leviticus 24:17-21; 1 Kings 21; Proverbs 19:5; Jeremiah 14:15; Matthew 5:38-39; 18:15-20; Revelation 11:3-7