1 John 4:3

Amplified Bible - Classic Edition

And every spirit which does not acknowledge and confess that Jesus Christ has come in the flesh [but would annul, destroy, sever, disunite Him] is not of God [does not proceed from Him]. This [nonconfession] is the [spirit] of the antichrist, [of] which you heard that it was coming, and now it is already in the world.

Cross References

Matthew 24:5

For many will come in (on the strength of) My name [appropriating the name which belongs to Me], saying, I am the Christ (the Messiah), and they will lead many astray.

1 John 2:18

Boys (lads), it is the last time (hour, the end of this age). And as you have heard that the antichrist [he who will oppose Christ in the guise of Christ] is coming, even now many antichrists have arisen, which confirms our belief that it is the final (the end) time.

1 John 2:22

Who is [such a] liar as he who denies that Jesus is the Christ (the Messiah)? He is the antichrist (the antagonist of Christ), who [habitually] denies and refuses to acknowledge the Father and the Son.

2 John 1:7

For many imposters (seducers, deceivers, and false leaders) have gone out into the world, men who will not acknowledge (confess, admit) the coming of Jesus Christ (the Messiah) in bodily form. Such a one is the imposter (the seducer, the deceiver, the false leader, the antagonist of Christ) and the antichrist.