Deuteronomy 18:21

And if you say in your heart, How shall we know the word which Jehovah has not spoken?

1 Thessalonians 5:24

Faithful is He who called you, who also will do it.

1 John 4:1-3

Beloved, do not believe every spirit, but try the spirits to see if they are of God, because many false prophets have gone out into the world.

Revelation 2:2

I know your works and your labor and your patience, and how you cannot bear those who are evil. And you tried those pretending to be apostles, and are not, and have found them 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
Faithful is He who called you, who also will do it.
1 John 4:1
Beloved, do not believe every spirit, but try the spirits to see if they are of God, because many false prophets have gone out into the world.
Revelation 2:2
I know your works and your labor and your patience, and how you cannot bear those who are evil. And you tried those pretending to be apostles, and are not, and have found them liars.