Matthew 18:16

but if he regard thee not, take with thee one or two more, that in the mouth of two or three witnesses every word may be established.

2 Corinthians 13:1

This, I say, is the third time I am coming to you: and at the mouth of two or three witnesses shall every word be established.

1 Timothy 5:19

Receive not an accusation against an elder, unless from two or three witnesses.

Hebrews 10:28

If any one that violateth the law of Moses, dieth without mercy under two or three witnesses,

John 8:17-18

And it is written in your own law, that the testimony of two persons is valid.

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

Matthew 18:16
but if he regard thee not, take with thee one or two more, that in the mouth of two or three witnesses every word may be established.
John 8:17
And it is written in your own law, that the testimony of two persons is valid.
2 Corinthians 13:1
This, I say, is the third time I am coming to you: and at the mouth of two or three witnesses shall every word be established.
1 Timothy 5:19
Receive not an accusation against an elder, unless from two or three witnesses.
Hebrews 10:28
If any one that violateth the law of Moses, dieth without mercy under two or three witnesses,