I once read John Frame write something about how the Incarnation of the Word triggers the explicit revelation of God as Trinity. God’s identity as Holy Trinity was present throughout the whole Old Testament, but it was not until “the only God, who is at the Father’s side” entered the world as a man and “made him known” that the glory of the Trinity was revealed with clarity. (John 1:18)
I think this is a true and important observation, and the truth of it is demonstrated in the opening narratives of Luke’s Gospel, where you suddenly find copious references to the Holy Spirit coming upon people in relation to the advent of the Son. One example is Zechariah. As he begins his song of praise in Luke 1:67, we read, “And his father Zechariah was filled with the Holy Spirit and prophesied, saying, ‘Blessed be the Lord God of Israel, for he has visited and redeemed his people, and has raised up a horn of salvation for us in the house of his servant David . . .” This is thoroughly Trinitarian worship. Zechariah may not be able to put all the pieces together at this point, but he is praising God the Father for sending God the Son, through God the Holy Spirit.
This is an appropriate response of praise to the coming of Christ, which is a work of the entire Trinity. Let us go and worship likewise!