In the first part of this paragraph in 1 Timothy Paul stated the “mystery of godliness is great.” He then defines what the mystery of godliness is in a series of confessional statements about Jesus. It is possible that each of these lines could be expanded more fully, unpacked from the brief three word statement into a short sermon. It is impossible to know for sure, but this short description of Jesus could have functioned like a creed. Many commentators observe these verses are likely an early church hymn or liturgy. We cannot know how any given early church gathering functioned, but it is not hard to imagine these lines repeated as a corporate confession of faith in who Jesus is.
Paul introduces these statements about Jesus with the word ὁμολογουμένως (homologouménōs). Although there is a significant textual variant which reads this as a verb, this is an adverb meaning “confessedly” or “undeniably” (BDAG), or “by common agreement, according to general consensus” (BrillDAG). Like the noun ὁμολογία, the word refers to an agreement or confession of allegiance. The word will eventually be used in the modern sense of a confession of faith such as the Nicene Creed.
Each statement is an aorist passive verb with a dative phrase (all with a preposition, except the third). Some take these as three pairs (NIV, NA26), with each pair contrasting heaven and earth. Others take the six items as two triads (ESV, NRSV),the first three lines focus on the life (and death) of Jesus and the vindication of the resurrection, the second triad focuses on his ongoing exaltation in the ascension and preaching of the gospel. Another option is that the six lines are chronological, from incarnation to Second Coming. The problem is that the final line is better associated with Pentecost than the second coming. (For a survey of the options, see Marshall, Pastoral Epistles, 500-2).
Manifest in the flesh. This short line refers to Jesus as God made flesh, the incarnation from birth to death. It is possible that this line only has post-resurrection appearances in mind, but it is not far from Phil 2:6-7, Jesus humbled himself to become human, “making himself nothing.”
Vindicated by the Spirit. While this could be a reference to the miracles Jesus did in the incarnation, it is more likely this is a reference to the resurrection. “Vindication” here has the sense of being proven right or innocent. While Jesus was executed as a sinner might be, God raised him from the dead, proving that he was in fact innocent.
Seen by angels. Consistent with the view that these phrases are post-resurrection, this may refer to the witness of the angels to the resurrection, or perhaps the exaltation of Jesus in heaven.
Proclaimed by the nations. This line refers to the ongoing mission of the church, presenting the gospel of Jesus to the world. Paul has in mind here his own mission of preaching the gospel to the Gentiles. LXX Ps 17:50 (18:49 ET) has a similar phrase, “I will give confess you among the nations, O Lord.” There are many texts in the Hebrew Bible which describe the nations coming to Zion in the future eschatological age (Isaiah 2, for example).
Believed on in the world. Paul refers to the success of the mission to the nations, the gospel is being believed by the “known world.” In the traditional view of the Pastoral epistles, he wrote this after his work in Rome; if the letters were written later it still refers to the success of the Pauline mission to the Gentiles; as the church continued to use this as a confession of faith it was even more true that the nations were responding in belief to the Gospel.
Taken up in glory. This final line seems to refer to the ascension, although chronologically this is out of order. The verb ἀναλαμβάνω (analambanō) appears in Acts 1:11, two angelic beings state that Jesus was “taken up into heaven.” The ascension obviously occurs well before the gospel was preached to the nations and believed by the world, but it is the climax of the events of Jesus’s life.
The mystery of godliness is therefore a statement about who Jesus is, what he did, and what the church continues to do after the ascension of Jesus. What Jesus has already done provides the basis for the ongoing mission of the church. By the time 1 Timothy was written, this would include preaching the Gospel throughout the Roman world.
This climactic statement about proper belief and proper conduct naturally draws Paul back to the main subject of the letter, the specific problem of the opponents in Ephesus. There are elders in Ephesus who are not conducting themselves in a way that is honorable within the household of God and they may very well have some defective view about who Jesus was or what he did.