“The Father loves the Son and has given all things into his hand” (v35). John the Baptist recognized that Jesus was a permanent turning point in human history. Prophets and teachers (and Temple rituals) had pointed the way, even John himself, but now “he who comes from heaven is above all” (v31). Jesus, God’s only Son, was the fulfillment of all God’s promises, the Word made flesh, and every other voice of truth and wisdom must “decrease” and lift up Jesus’ name (v30).
“This joy of mine is now complete” (v29). The past (the law and prophets) was important, but it was incomplete; Jesus is here, and He is everything.