Matthew 18:16

But if he does not listen to you, take along with you one or two others, so as to have every word confirmed by the testimony of two or three witnesses. If he refuses to listen to them, report it to the church.

2 Corinthians 13:1

This is my third visit to you. Any charge preferred must be sustained by the evidence of two or three witnesses.

John 8:17

Even in your own law it is written, 'The testimony of two persons is true.'

1 Timothy 5:19

Make it a rule not to consider a charge preferred against an elder, unless it is supported by two or three witnesses.

Hebrews 10:28

Anyone who breaks the law of Moses pays the death penalty without any show of pity, on the evidence of two or three witnesses only.

Matthew 26:60-61

but they could not, although many false witnesses came forward to testify. At last two men came forward

Revelation 11:3-7

And I will permit my two witnesses, clothed in sackcloth, to prophesy for one thousand, two hundred and sixty days."

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 does not listen to you, take along with you one or two others, so as to have every word confirmed by the testimony of two or three witnesses. If he refuses to listen to them, report it to the church.
Matthew 26:60
but they could not, although many false witnesses came forward to testify. At last two men came forward
John 8:17
Even in your own law it is written, 'The testimony of two persons is true.'
2 Corinthians 13:1
This is my third visit to you. Any charge preferred must be sustained by the evidence of two or three witnesses.
1 Timothy 5:19
Make it a rule not to consider a charge preferred against an elder, unless it is supported by two or three witnesses.
Hebrews 10:28
Anyone who breaks the law of Moses pays the death penalty without any show of pity, on the evidence of two or three witnesses only.
Revelation 11:3
And I will permit my two witnesses, clothed in sackcloth, to prophesy for one thousand, two hundred and sixty days."

General references

John 7:51
"Our law does not condemn a man before it hears what he has to say and finds out what he is doing, does it?"