Deuteronomy 18:21

You may say to yourself, ‘How can we recognize a message the Lord has not spoken?’

1 Thessalonians 5:24

He who calls you is faithful, who also will do it.

1 John 4:1-3

Dear friends, do not believe every spirit, but test the spirits to determine if they are from God, because many false prophets have gone out into the world.

Revelation 2:2

I know your works, your labor, and your endurance, and that you cannot tolerate evil. You have tested those who call themselves apostles and are not, and you have found them to be liars.

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, who also will do it.
1 John 4:1
Dear friends, do not believe every spirit, but test the spirits to determine if they are from God, because many false prophets have gone out into the world.
Revelation 2:2
I know your works, your labor, and your endurance, and that you cannot tolerate evil. You have tested those who call themselves apostles and are not, and you have found them to be liars.

Holman Christian Standard Bible®, Copyright © 1999, 2000, 2002, 2003, 2009 by Holman Bible Publishers.