This verse is sometimes cited to suggest that Jesus himself is God. The main problem here however is that Greek texts don’t all agree. Some have “God”, some have “he”, which could still mean God was revealed, or could mean that Jesus himself was revealed.
Authorized version “God” vs. modern version “He”?
The KJV follows the received majority text
And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels, preached unto the Gentiles, believed on in the world, received up into glory. (1 Timothy 3:16, KJV)
The NRSV, and most other modern versions, follow the older minority manuscripts
Without any doubt, the mystery of our religion is great: He was revealed in flesh, vindicated in spirit, seen by angels, proclaimed among Gentiles, believed in throughout the world, taken up in glory. (1 Timothy 3:16, NRSV)
The committee which assembles the standard Greek text used by the United Bible Societies publishes a slim brown volume called A Textual Commentary on the Greek New Testament which explains why the committee has preferred certain readings considers that the original text read “he” and that “God” arose either as a mistake or deliberately:
…all ancient versions presuppose hos or ho ; and no patristic writer prior to the last third of the fourth century testifies to the reading theos. The reading theos arose either (a) accidentally, or (b) deliberately, either to supply a substantive for the following six verbs, or, with less probability, to provide greater dogmatic precision… (Bruce Metzger, et.al. 2006)
Assuming the text originally said ‘he’…
If the text, as the UBS committee believe, originally read: “He was revealed in flesh” then that fits well with “vindicated in spirit, seen by angels, proclaimed among Gentiles, believed in throughout the world, taken up in glory” – all of which can only really apply to Jesus and not to God.
It is also worth noting here that the idea of “flesh” (Greek sarx), as elsewhere in the New Testament, is not about “Jesus appeared in a body” (which would be Greek soma) but saying that Jesus appeared in human nature (sarx), in other words that Christ was a man “tempted like us” in all points. (Hebrews 2:14, 4:15, 5:7-10).
Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God (1 John 4:2, KJV)
This does not mean that every person who accepted that Jesus came in a body (soma) was of God; even Pilate and Caiaphas accepted that Jesus had a body (soma) or they would not have conspired to crucify him.
But if the text originally said ‘God’…
However even if the text as in the KJV is authentic and not an error or deliberate change, the verse still does not say that Jesus is God. “God was manifest in the flesh” (ἐφανερώθη ἐν σαρκί) would not naturally mean that God disguised himself as Jesus, the passage would only mean that Christ revealed his Father. This is something we already know from many other Bible verses. And with this Greek verb (φανερόω), much like equivalent English verbs, when A reveals B, that does not mean that A is B. If A is B, then it cannot show, reveal, or manifest B.
For more on the quite Biblical idea of Jesus revealing God see “Whoever has seen me has seen the Father” : Did Jesus claim to be God to Philip?