Deuteronomy 17:6

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

Numbers 35:30

‘If anyone kills a person [intentionally], the murderer shall be put to death on the testimony of [two or more] witnesses; but no one shall be put to death on the testimony of [only] one witness.

Deuteronomy 19:15

“A single witness shall not appear in a trial against a man for any wrong or any sin which he has committed; [only] on the testimony or evidence of two or three witnesses shall a charge be confirmed.

Matthew 18:16

But if he does not listen, take along with you one or two others, so that every word may be confirmed by the testimony of two or three witnesses.

2 Corinthians 13:1

This is the third time that I am visiting you. Every fact shall be sustained and confirmed by the testimony of two or three witnesses.

1 Timothy 5:19

Do not accept an accusation against an elder unless it is based on [the testimony of at least] two or three witnesses.

Hebrews 10:28

Anyone who has ignored and set aside the Law of Moses is put to death without mercy on the testimony of two or three witnesses.

John 8:17-18

Even in your own law it is written that the testimony of two persons is true [valid and admissible].

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 appear in a trial against a man for any wrong or any sin which he has committed; [only] on the testimony or evidence of two or three witnesses shall a charge be confirmed.
Numbers 35:30
‘If anyone kills a person [intentionally], the murderer shall be put to death on the testimony of [two or more] witnesses; but no one shall be put to death on the testimony of [only] one witness.
Matthew 18:16
But if he does not listen, take along with you one or two others, so that every word may be confirmed by the testimony of two or three witnesses.
John 8:17
Even in your own law it is written that the testimony of two persons is true [valid and admissible].
2 Corinthians 13:1
This is the third time that I am visiting you. Every fact shall be sustained and confirmed by the testimony of two or three witnesses.
1 Timothy 5:19
Do not accept an accusation against an elder unless it is based on [the testimony of at least] two or three witnesses.
Hebrews 10:28
Anyone who has ignored and set aside the Law of Moses is put to death without mercy on the testimony of two or three witnesses.