Deuteronomy 19:15

A single witness shall not rise up against a man on account of any iniquity or any sin which he has committed; on the evidence of two or three witnesses a matter shall be confirmed.

Numbers 35:30

If anyone kills a person, the murderer shall be put to death at the evidence of witnesses, but no person shall be put to death on the testimony of one witness.

Matthew 18:16

But if he does not listen to you, take one or two more with you, so that by the mouth of two or three witnesses every fact may be confirmed.

2 Corinthians 13:1

This is the third time I am coming to you. Every fact is to be confirmed by the testimony of two or three witnesses.

Deuteronomy 17:6

On the evidence of two witnesses or three witnesses, he who is to die shall be put to death; he shall not be put to death on the evidence of one witness.

John 8:17

Even in your law it has been written that the testimony of two men is true.

1 Timothy 5:19

Do not receive an accusation against an elder except on the basis of two or three witnesses.

Hebrews 10:28

Anyone who has set aside the Law of Moses dies without mercy on the testimony of two or three witnesses.

1 Kings 21:10

and seat two worthless men before him, and let them testify against him, saying, ‘You cursed God and the king.’ Then take him out and stone him to death.”

1 Kings 21:13

Then the two worthless men came in and sat before him; and the worthless men testified against him, even against Naboth, before the people, saying, “Naboth cursed God and the king.” So they took him outside the city and stoned him to death with stones.

Matthew 26:60-61

They did not find any, even though many false witnesses came forward. But later on two came forward,

Revelation 11:3-7

And I will grant authority to my two witnesses, and they will prophesy for 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.

Bible References

At the mouth

Deuteronomy 17:6
On the evidence of two witnesses or three witnesses, he who is to die shall be put to death; he shall not be put to death on the evidence of one witness.
Numbers 35:30
If anyone kills a person, the murderer shall be put to death at the evidence of witnesses, but no person shall be put to death on the testimony of one witness.
1 Kings 21:10
and seat two worthless men before him, and let them testify against him, saying, ‘You cursed God and the king.’ Then take him out and stone him to death.”
Matthew 18:16
But if he does not listen to you, take one or two more with you, so that by the mouth of two or three witnesses every fact may be confirmed.
Matthew 26:60
They did not find any, even though many false witnesses came forward. But later on two came forward,
John 8:17
Even in your law it has been written that the testimony of two men is true.
2 Corinthians 13:1
This is the third time I am coming to you. Every fact is to be confirmed by the testimony of two or three witnesses.
1 Timothy 5:19
Do not receive an accusation against an elder except on the basis of two or three witnesses.
Hebrews 10:28
Anyone who has set aside the Law of Moses dies without mercy on the testimony of two or three witnesses.
Revelation 11:3
And I will grant authority to my two witnesses, and they will prophesy for twelve hundred and sixty days, clothed in sackcloth.”

General references

Numbers 35:30
If anyone kills a person, the murderer shall be put to death at the evidence of witnesses, but no person shall be put to death on the testimony of one witness.
Deuteronomy 17:6
On the evidence of two witnesses or three witnesses, he who is to die shall be put to death; he shall not be put to death on the evidence of one witness.
John 7:51
Our Law does not judge a man unless it first hears from him and knows what he is doing, does it?”