Book of 1 John Chapter 4 Vs. 3

 Test the Spirits

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."

is come in the flesh

Omit. Render, confesseth not Jesus. So Rev. An ancient reading is λύει τὸν Ἱησοῦν annulleth or destroyeth Jesus.” The simple Jesus emphasizes the humanity of our Lord considered in itself. See Rom. 3:26; 10:9; 2Cor. 11:4; Eph. 4:21; Heb. 2:9.

that spirit of... These false teachers who denied the true nature of the Son are to be identified among the antichrists in 2:28-29 (2 John 7). The same demonic deception that will work to produce the final world ruler who rules as the false Christ is always actively seeking to distort Jesus Christ's true nature, perverting the gospel.

and this is (τοῦτο)

Not this spirit, but this non-confession, summed up in all its manifestations.

The final Antichrist will not be something new but will be the ultimate embodiment of all the antichrist spirits that have perverted truth and propagated satanic lies since the beginning. This is similar to 2 Thes. 2:3-8, where the man of lawlessness (Antichrist) is still to be revealed, but the mystery of lawlessness is already at work.

 

and even now... Satan who will produce the future Antichrist is now in the world (2Thes. 2:1-12). He already is producing many antichrists (see 1Jhn. 2:18-22).

cometh (ἔρχεται)

The prophetic present, equivalent to is about to come. The same term is used of Christ (John 14:3; 21:22; Rev. 22:20).

The terrible thing is that many churches teach that Jesus was nothing more than a man when He walked on the earth. You can easily see this is a dangerous message to bring. We cannot think of Jesus as just another man. He is divine in nature. 

The divinity of Christ has been a question for years. That is what separates the true believers from those who would be against Christ. The true believers believe Jesus was God manifest in the flesh. Even to believe He became God at resurrection, would be classified as those opposed to God. 

An anti-Messiah or "antichrist" is coming. See 2Ths. 2:3 on the Man of Lawlessness and his role in the drama of End-Time history; see also Revelation 12-13. Yochanan is less concerned with this unique anti-Messianic figure than with the practical danger to believers from the many anti-Messiahs who went out from us, but they weren't part of us, who deny that Yeshua is the Messiah (1Jhn. 2:22-23) or that he came as a flesh-and-blood human being (1Jhn. 4:2-3, 2Jhn. 1:7). See also 1Jhn. 3:7-10. 

To begin with, the Spirit of God must be distinguished from false spirits. This is particularly necessary because many false prophets have gone out into the world. The touchstone by which these spirits false prophets are to be tested is their attitude toward the incarnate person of Jesus Christ. The failure to acknowledge homologei, confess; cf. 1Jhn. 1:9; 2:23; 4:15) that Jesus Christ has come in the flesh is precisely what exposes the spirit of the antichrist, which John had already warned his readers about (1Jhn. 2:18-27; cf. 2Jhn. 1:7).

Philippians 2:10 "That at the name of Jesus every knee should bow, of things in heaven, and things in earth, and things under the earth;"

This alone, makes you know He is deity.