1 John 5:8
the Spirit, and the water, and the blood; and the three agree in one.
But if he do not hear thee, take with thee one or two besides, that every matter may stand upon the word of two witnesses or of three.
One witness shall not rise up against a man for any iniquity, and 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.
2 Corinthians 13:1
This third time I am coming to you. In the mouth of two or three witnesses shall every matter be established.
1 Timothy 5:19
Against an elder receive not an accusation unless where there are two or three witnesses.
Any one that has disregarded Moses' law dies without mercy on the testimony of two or three witnesses:
At the mouth of two witnesses, or three witnesses, shall he that is to die be put to death: he shall not be put to death at the mouth of one witness.