'Witnesses' in the Bible

At the mouth of two witnesses, or three witnesses, shall he that is to die be put to death; at the mouth of one witness he shall not be put to death.

The hand of the witnesses shall be first upon him to put him to death, and afterward the hand of all the people. So thou shalt put away the evil from the midst of thee.

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.