Deuteronomy 19:15

One witness I shall not rise up, against a man for any iniquity, or for any sin, with regard to any sin that he may commit, - at the mouth of two witnesses or at the mouth of three witnesses, must a matter be establish.

Numbers 35:30

Whosoever taketh away life, at the mouth of witnesses, shall, the slayer be slain, - but, one witness, shall not testify against a person, to put him to death.

Matthew 18:16

But, if he do not hearken, take with thee, yet one or two, that, at the mouth of two witnesses or three, every declaration, maybe established;

2 Corinthians 13:1

This third time, am I coming unto you: - at the mouth of two witnesses, or three, shall every matter be established.

Deuteronomy 17:6

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

John 8:17

And, in your own law, it is written, that, two men's witness, is, true:

1 Timothy 5:19

Against an elder, entertain not, an accusation, except at, the mouth of two, or three, witnesses;

Hebrews 10:28

Any one having set aside a law of Moses, apart from compassions, upon the testimony of two or three witnesses, dieth:

1 Kings 21:10

then let two reckless men take their seats before him, that they may bear witness against him, saying, Thou hast reviled God and king! then shall ye carry him forth and stone him, that he die.

1 Kings 21:13

Then came in the two reckless men, and sat before him, and the men bare witness against him, even against Naboth, before the people, saying, Naboth hath reviled God and king! So they carried him forth, outside the city, and stoned him with stones, that he died.

Matthew 26:60-61

and found not any, though many came forward as false-witnesses. At length, however, there came forward, two,

Revelation 11:3-7

And I will give unto my two witnesses, that they shall prophesy, a thousand two hundred and sixty days, arrayed 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
At the mouth of two witnesses or three witnesses, shall he that is to die be put to death, - he shall not be put to death at the mouth of one witness.
Numbers 35:30
Whosoever taketh away life, at the mouth of witnesses, shall, the slayer be slain, - but, one witness, shall not testify against a person, to put him to death.
1 Kings 21:10
then let two reckless men take their seats before him, that they may bear witness against him, saying, Thou hast reviled God and king! then shall ye carry him forth and stone him, that he die.
Matthew 18:16
But, if he do not hearken, take with thee, yet one or two, that, at the mouth of two witnesses or three, every declaration, maybe established;
Matthew 26:60
and found not any, though many came forward as false-witnesses. At length, however, there came forward, two,
John 8:17
And, in your own law, it is written, that, two men's witness, is, true:
2 Corinthians 13:1
This third time, am I coming unto you: - at the mouth of two witnesses, or three, shall every matter be established.
1 Timothy 5:19
Against an elder, entertain not, an accusation, except at, the mouth of two, or three, witnesses;
Hebrews 10:28
Any one having set aside a law of Moses, apart from compassions, upon the testimony of two or three witnesses, dieth:
Revelation 11:3
And I will give unto my two witnesses, that they shall prophesy, a thousand two hundred and sixty days, arrayed in sackcloth.

General references

Numbers 35:30
Whosoever taketh away life, at the mouth of witnesses, shall, the slayer be slain, - but, one witness, shall not testify against a person, to put him to death.
Deuteronomy 17:6
At the mouth of two witnesses or three witnesses, shall he that is to die be put to death, - he shall not be put to death at the mouth of one witness.
John 7:51
Surely, our law, doth not judge the man, unless it hear first from him, and get to know what he is doing?