Paul wasn’t there at the birth of Christ, but Paul makes it clear who Jesus is when writing to Timothy:
I hope to come to you soon, but I am writing these things to you so that, if I delay, you may know how one ought to behave in the household of God, which is the church of the living God, a pillar and buttress of the truth. Great indeed, we confess, is the mystery of godliness: He was manifested in the flesh, vindicated by the Spirit, seen by angels, proclaimed among the nations, believed on in the world, taken up in glory. 1 Timothy 3:14-16
To whom does the church belong? It belongs to Christ: Matthew 16:18
Whose church is it? Paul says it is the church of the living God!
Who is this Jesus that we celebrate? He is One who came in the flesh to save us from our sins.
Thank you, Jesus, for coming and saving us.