1 John 4:3
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. 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.
The verse gives a test for identifying spirits: every spirit that does not confess that Jesus Christ has come in the flesh is not of God, and this is the spirit of antichrist, which was already in the world. God's word is the rule for testing spiritual claims and distinguishing truth from error, distinguishing the Spirit of God from the spirit of error. Confessing Christ's incarnation is a divinely appointed test of spirits and of anyone claiming the gift of prophecy, so that accepting or rejecting this truth tests that claim. The test is to be used amid the perils of the last days because many false prophets have gone out into the world, and it is to be spoken with the power of a living Christ and with the grace given to those striving lawfully for every victory when rescuing souls that have been helping Dr. Kellogg to stand where he now stands.
In John's later years the growing church was in peril from satanic delusion, opposition to the doctrines of Christ, dissension and heresy, skepticism, and deceptive doctrines. Not confessing that Jesus Christ has come in the flesh includes pretending to be true to God's cause while in practice denying Christ and His gospel by living in transgression of the divine law and bringing heresy into the church. It also includes teaching that Christ was only a good man while denying His divinity, claiming that His love releases those who profess Him from obedience to the law of God, and teaching on the other hand that Jewish customs and ceremonies must be kept and that mere observance of the law without faith in the blood of Christ is sufficient for salvation.
Denial of Christ's divinity is an expression of this antichrist spirit, and skepticism and rejection of divine truth are associated with it. Skepticism, including infidelity and belief in Spiritualism's lying wonders, belongs to this class, and pride, ignorance of God's character, ambition, and love of sin lead people to deny Christ and reject the Bible, seeking to escape accountability to God. The spirit of antichrist works through false prophets to seduce believers from the truth by spiritualistic suppositions and fables clothed in the garments of truth, captivating the minds of those not established in present truth, and its sentiments are of the world, worldly in spirit and character, producing false representations of God.
The spirit of antichrist is opposed to God and Christ and is not of God, and it prevails greatly and is widespread amid moral darkness when people who appear to live by God's Spirit or to have divine life instead oppose the truth they claim to present and profess to present the truth while actually working against it. The verse's language about antichrist applies to the rival popes, in that Wycliffe urged people to consider whether both priests were truthfully condemning each other as antichrist, with the fiend reigning in two priests rather than one. The verse calls for faithful and earnest testimony for the Lord upon every suitable occasion against such deceivers, and protection comes by watching unto prayer, walking and working in constant dependence on God, having Christ formed in the heart as the hope of glory to enlighten, sanctify and strengthen, and by holding to the teaching of the apostles without setting it aside or speaking disrespectfully of it.