v. 30b-31 ...and I was daily his delight, rejoicing before him always, rejoicing in his inhabited world and delighting in the human race.
The speaker here is Wisdom, who , in the passage, was said to be "before the beginning of the earth" and at the creation "beside [the LORD] like a master builder."
When John was trying to give voice to "the Word made flesh," among the sources into which he reached was the Wisdom tradition of the Hebrew Scriptures. Wisdom (a feminine word in Hebrew, so always referred to as "she") was a companion of the divine from the beginning, an agent of God's activity in creation, but also at such remarkable times as the Exodus. She is said to be God's presence in his people Israel.
John (and other New Testament writers) used language about Wisdom to talk about Jesus, especially his existence before his birth, as "the cosmic Christ," who, as John says in John 1, was "in the beginning" and "through whom all things came into being."
The verse cited above is a marvelous piece of writing, managing to cram the words "delight" and "rejoice" twice each into the half sentence. Wisdom is the delight of God, but, in turn, delights in God's creation as well. She rejoices in God, but rejoices, too, in "the inhabited world." This is very much a "Jesus message" and a "Christmas message." What we call the "incarnation" makes Wisdom's rejoicing and delighting all the stronger. God/Wisdom has delighted so much in creation that he has joined it. Jesus is Wisdom incarnate.
Let us share in this "double delight." Let us delight in the God of Christmas, and delight in the world into which he has entered.