After all the people had been baptized and Jesus also had been baptized and was praying, heaven was opened and the Holy Spirit descended upon him in bodily form like a dove. And a voice came from heaven, "You are my beloved Son; with you I am well pleased."
From those who were there to witness the baptism of our Lord and record it for us to know how pleased God is with his Son. It's a beautiful thing to read about how pleased God is about his Son. To appear in the form of a dove with a voice coming from heaven, awesome.
Do you think our own parent's wouldn't do that for us when we have done something to please them. They love us, so why wouldn't they too go to great lengths to let us know how well we have done. Many parent's have done this to acknowledge their child's worth in their eyes.
Without realizing how much we do imitate our own heavenly parent's their role in our lives. How their gift of baptism by water cleanses us of original sin and prepares us for the gift of the Spirit. Let it be our prayer that we too shall begin to acknowledge what God has done for us by sending his Son.