Deuteronomy 18:21

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

Cross References

1 Thessalonians 5:24 Faithful is he that calleth you, who also will do it.
1 John 4:1-3 Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world. Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God: And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that spirit of antichrist, whereof ye have heard that it should come; and even now already is it in the world.
Revelation 2:2 I know thy works, and thy labour, and thy patience, and how thou canst not bear them which are evil: and thou hast tried them which say they are apostles, and are not, and hast found them liars: