Deuteronomy 19:15

A lone witness is not sufficient to establish any wrongdoing or sin against a man, regardless of what offense he may have committed. A matter must be established by the testimony of two or three witnesses.

Note Cited in Matthew 18:16 and 2 Corinthians 13:1

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.

One witness shall not rise up against a man for any iniquity, or for any sin that he sins. At the mouth of two witnesses, or at the mouth of three witnesses, shall a matter be established.

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 a matter be established.