Matthew 18:16

and if he may not hear, take with thee yet one or two, that by the mouth of two witnesses or three every word may stand.

Deuteronomy 19:15

'One witness doth not rise against a man for any iniquity, and for any sin, in any sin which he sinneth; by the mouth of two witnesses, or by the mouth of three witnesses, is a thing established.

John 8:17

and also in your law it hath been written, that the testimony of two men are true;

2 Corinthians 13:1

This third time do I come unto you; on the mouth of two witnesses or three shall every saying be established;

1 Timothy 5:19

Against an elder an accusation receive not, except upon two or three witnesses.

Hebrews 10:28

any one who did set at nought a law of Moses, apart from mercies, by two or three witnesses, doth die,

Numbers 35:30

whoso smiteth a person, by the mouth of witnesses doth one slay the murderer; and one witness doth not testify against a person -- to die.

Deuteronomy 17:6

By the mouth of two witnesses or of three witnesses is he who is dead put to death; he is not put to death by the mouth of one witness;

1 Kings 21:13

and two men -- sons of worthlessness -- come in, and sit over-against him, and the men of worthlessness testify of him, even Naboth, before the people, saying, 'Naboth blessed God and Melech;' and they take him out to the outside of the city, and stone him with stones, and he dieth;

1 John 5:7-8

because three are who are testifying in the heaven, the Father, the Word, and the Holy Spirit, and these -- the three -- are one;

Revelation 11:3

and I will give to My two witnesses, and they shall prophesy days, a thousand, two hundred, sixty, arrayed with sackcloth;

Treasury of Scripture Knowledge

Summary

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

General references

Bible References

That in

Numbers 35:30
whoso smiteth a person, by the mouth of witnesses doth one slay the murderer; and one witness doth not testify against a person -- to die.
Deuteronomy 17:6
By the mouth of two witnesses or of three witnesses is he who is dead put to death; he is not put to death by the mouth of one witness;
Deuteronomy 19:15
'One witness doth not rise against a man for any iniquity, and for any sin, in any sin which he sinneth; by the mouth of two witnesses, or by the mouth of three witnesses, is a thing established.
1 Kings 21:13
and two men -- sons of worthlessness -- come in, and sit over-against him, and the men of worthlessness testify of him, even Naboth, before the people, saying, 'Naboth blessed God and Melech;' and they take him out to the outside of the city, and stone him with stones, and he dieth;
John 8:17
and also in your law it hath been written, that the testimony of two men are true;
2 Corinthians 13:1
This third time do I come unto you; on the mouth of two witnesses or three shall every saying be established;
1 Timothy 5:19
Against an elder an accusation receive not, except upon two or three witnesses.
Hebrews 10:28
any one who did set at nought a law of Moses, apart from mercies, by two or three witnesses, doth die,
1 John 5:7
because three are who are testifying in the heaven, the Father, the Word, and the Holy Spirit, and these -- the three -- are one;
Revelation 11:3
and I will give to My two witnesses, and they shall prophesy days, a thousand, two hundred, sixty, arrayed with sackcloth;

General references

Numbers 35:30
whoso smiteth a person, by the mouth of witnesses doth one slay the murderer; and one witness doth not testify against a person -- to die.
Deuteronomy 17:6
By the mouth of two witnesses or of three witnesses is he who is dead put to death; he is not put to death by the mouth of one witness;