“By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God;”This is a significant verse validating the all important truth of Jesus humanity, as clearly taught elsewhere in the Scriptures. Traditionally, it has been understood as an argument against the docetic gnostics (“docetism" - from docetae, meaning “to appear”), in which it was asserted that Jesus was not truly flesh and blood, but only "appeared" to be human. Since John uses the phrase "in the flesh" and warns, in verse 3, that the spirit of antichrist is already in the world (1 John 4:3), it seems very likely that this is what John was thinking here. However, I suggest that John had something more in mind than an argument against docetism only!
--1 John 4:2 (NASB)
We must not allow pre-conceived notions to define what John means by "Jesus Christ has come in the flesh". The AMP and NCV bibles both slant the verse to make it sound as if John supported the traditional doctrine of incarnation - that Jesus pre-existed in heaven, came to earth, and took on flesh. For example, the AMP says "every spirit that acknowledges ... that Jesus ... has become man and has come in the flesh ..." This translation boldly suggests that Jesus was something other than human prior to being born. The NCV puts it even stronger saying, "... every spirit that confesses that Jesus Christ came to earth as a human..." This really goes beyond the bounds of the original lanquage. In both of these bible versions the translators project their own preconceptions about Jesus’ pre-existence onto the Greek text! Thankfully, none of the other major versions take such liberties with the text. Instead, they stick to the simple reading "come in the flesh".
So what does it mean to, "come in the flesh"?
The word "come" is erchomai (perfect tense), denoting something that has been completed in the past, once and for all, not needing to be repeated. In other words, it happened and has not been reversed or changed – it is still in force – Jesus was born human and remains human. This could be a specific reference to Jesus birth. I am not aware of any scholars or commentaries that share this opinion, but that doesn't mean it’s wrong. Just consider what I say here, and you be the judge.
The language employed here (has come) should not be construed as meaning 'has come from heaven'! Yet, this is exactly where most scholarship seems to go. The fact is, to say one "has come" does not have to refer to movement from one place to another. It can be be used metaphorically as well! For example, the Bible also says that John "came neither eating nor drinking" (Matt 11:18, also see Matt 21:32). It's the same thing! No one understands this to mean that John came from any particular place. It simply refers to the fact that John "showed up" doing what he was called to do (preaching his message of repentance) in a simple an unpretentious way. Further, and perhaps more precisely, John himself uses this kind of language while in prison. Expressing doubt about whether Jesus was the the Messiah that Israel was waiting for, he sent messengers to inquire of Jesus, “Are you the one who is to come, or do we look for another?” (Matt 11:3) This was a way of speaking of the expected Messiah! He was to “come” in the sense that he was a promise to be fulfilled – a man through whom God would work in a mighty way to bring deliverance to Israel.
The fact that John adds the phrase "in the flesh" emphasizes not merely Jesus' human nature, but the fact that his body was really human. This would speak not only to docetic ideas, but other heresies as well, including that of Cerinthus who believed the man Jesus and the Christ were separate entities. The Cerinthian heresy taught that the Christ was the “Divine Spirit” who temporarily entered Jesus, the man, at his baptism and left him at his crucifixion.
It is vital to see that John is not speaking only of Jesus, the man, but of Jesus, the Christ (the Messiah). In the Lexham translation of the Bible, the note on this verse suggests the alternate reading "every spirit that confesses Jesus as Christ who has come in the flesh." This is also the way the NET bible reads and, in my opinion, is the correct rendering because it clearly associates Jesus as the Christ. This goes back to 1John 2:22 where the warning is "who is the liar but the one who denies that Jesus is the Christ?" (Also, see John 9:22) To me, John is clearly saying that Jesus and the Christ are one and the same, and that he was a genuine flesh and blood human being. And I would further suggest that John may have had in mind Jesus’ lineage. The Jews did, after all, expect one to come who would be like Moses, and who would be from the line of David.
In every prophecy foretelling Messiah's coming, it was never suggested or even hinted at, that he would be God. The expectation of Messiah was that he would be a man - a man chosen by God, anointed of God, without sin, but nonetheless a man (See Matt 11:3; Acts 2:22; 1Tim 2:5; Heb 4:15) Yet, in virtually every commentary on this verse, both classic and modern, it is suggested that John claims Jesus to be both human and Deity. Where exactly does the text say that Jesus is Deity? Where does the bible ever say that Christ and God are the same, or equal? Nowhere!! Christ is not Jesus last name, and it is NOT a synonym for God!
Given John's own stated purpose for writing in John 20:31, "that you may believe that Jesus is the Son of God" (another title for the Christ), It seems unlikely that he would argue from a Trinitarian point of view. John was saying, in a most emphatic way, that the Messiah Jesus, was a real human being with a traceable genealogy. In this way, he argued not only against the docetist’s and other heretical groups such as that of Cerinthus, but perhaps even those ideas which eventually came to be known as orthodoxy, attributing a second (divine) nature to Jesus!