Deuteronomy 18:21

And if you say in your heart, 'How may we know the word that the LORD has not spoken?'--

1 Thessalonians 5:24

He who calls you is faithful; he will surely do it.

1 John 4:1-3

Beloved, do not believe every spirit, but test the spirits to see whether they are from God, for many false prophets have gone out into the world.

Revelation 2:2

"'I know your works, your toil and your patient endurance, and how you cannot bear with those who are evil, but have tested those who call themselves apostles and are not, and found them to be false.

Treasury of Scripture Knowledge

Summary

And if thou say in thine heart, How shall we know the word which the LORD hath not spoken?

Bible References

General references

1 Thessalonians 5:24
He who calls you is faithful; he will surely do it.
1 John 4:1
Beloved, do not believe every spirit, but test the spirits to see whether they are from God, for many false prophets have gone out into the world.
Revelation 2:2
"'I know your works, your toil and your patient endurance, and how you cannot bear with those who are evil, but have tested those who call themselves apostles and are not, and found them to be false.

The Holy Bible, English Standard Version® copyright © 2001 by Crossway Bibles, a publishing ministry of Good News Publishers.