Matthew 18:16

But if he will not hear, take with thee one or two more, that by the mouth of two or three witnesses every word may be established.

2 Corinthians 13:1

I am coming to you this third time: every word shall be established by the mouth of two or three witnesses.

John 8:17

Even in your law it is written, The testimony of two men is valid.

1 Timothy 5:19

Against an elder receive not an accusation, unless by two or three witnesses.

Hebrews 10:28

He that despised the law of Moses died without mercy, under two or three witnesses.

Matthew 26:60-61

to put him to death, But found none; yea, tho' many false witnesses came, yet found they none.

Revelation 11:3-7

And I will give to my two witnesses to prophesy twelve hundred and sixty days, clothed in sackcloth.

Treasury of Scripture Knowledge

Summary

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.

General references

Bible References

At the mouth

Matthew 18:16
But if he will not hear, take with thee one or two more, that by the mouth of two or three witnesses every word may be established.
Matthew 26:60
to put him to death, But found none; yea, tho' many false witnesses came, yet found they none.
John 8:17
Even in your law it is written, The testimony of two men is valid.
2 Corinthians 13:1
I am coming to you this third time: every word shall be established by the mouth of two or three witnesses.
1 Timothy 5:19
Against an elder receive not an accusation, unless by two or three witnesses.
Hebrews 10:28
He that despised the law of Moses died without mercy, under two or three witnesses.
Revelation 11:3
And I will give to my two witnesses to prophesy twelve hundred and sixty days, clothed in sackcloth.

General references

John 7:51
Doth our law judge a man before it hear him, and know what he doth?