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.

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.

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.

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.

John 8:17-18

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

Treasury of Scripture Knowledge

Summary

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

Bible References

General references

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.
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.