Deuteronomy 18:21

And if thou say in thy heart, How shall we know the word that Jehovah hath not spoken?

1 Thessalonians 5:24

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

1 John 4:1-3

Beloved, believe not every spirit, but prove the spirits, if they are of God; because many false prophets are gone out into the world.

Revelation 2:2

I know thy works and thy labour, and thine endurance, and that thou canst not bear evil men; and thou hast tried them who say that themselves are apostles and are not, and hast 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
He is faithful who calls you, who will also perform it.
1 John 4:1
Beloved, believe not every spirit, but prove the spirits, if they are of God; because many false prophets are gone out into the world.
Revelation 2:2
I know thy works and thy labour, and thine endurance, and that thou canst not bear evil men; and thou hast tried them who say that themselves are apostles and are not, and hast found them liars;