Now when all the people were baptized, and when Jesus also had been baptized and was praying, the heavens were opened, and the Holy Spirit descended on him in bodily form, like a dove; and a voice came from heaven, "You are my beloved Son; with you I am well pleased."
The baptism of Jesus served as a powerful validation of the person of Jesus. Luke gives us much historical detail to root the start of Jesus’ public ministry in historical data. In fact, Luke 3:1-2 anchors these events securely in known historical details that are easily verified outside of biblical sources. Those liberal scholars with an agenda against the text who want to consider the content of the gospels to be second or third century legend have to deal with the fact that Luke lived close enough to these events to be able to carefully show the “news headlines” of the time in which they began. And he is accurate.
It is at the baptism of Jesus that we get a clear trinitarian representation of the Godhead. God the Father validates God the Son as the Holy Spirit of God descends on him “in bodily form”. This is pretty dramatic stuff. All three members of the Trinity can be verified by the human senses in this account. Jesus can be seen, heard, touched. The Spirit of God is seen. The voice of the Father is heard.
The gospel of Luke is a treasure trove for presenting the gospel to the modern empiricist. These are tough accounts to dismiss. It is one reason why C.S. Lewis was “dragged into the kingdom kicking and screaming”. He became convinced that Jesus was Who He said He was by a thorough reading of the gospels. This was a man who was an intellectual agnostic and thoroughly trained in the analysis of ancient myth at the doctorate level. And Lewis was convinced that the gospels read like history. He was finally convinced that it would be logically inconsistent to dismiss Jesus as merely legend.
Jesus began His ministry at a real time and a real place. And a supernatural event occurred in the midst of those real events. At a time thoroughly anchored in real space-time, Jesus began to preach the good news, heal the sick, call people to Himself, and the world has been changed. It is still being changed by Jesus because the story of the good news is still going forward. He is living in me and working in me and through me in a real time and place at this moment. He is doing so through His followers right now. His baptism only began the public transformation that has been ongoing for two thousand years.