When Jesus Christ was preparing to start his public ministry work on Earth, the Bible says, the prophet John the Baptist baptized him in the Jordan River and miraculous signs of Jesus' divinity took place: The Holy Spirit appeared in the form of a dove, and God the Father's voice spoke from heaven. Here's a summary of the story from Matthew 3:3-17 and John 1:29-34, with commentary:
Preparing the Way for the World's Savior
Matthew chapter begins by describing how John the Baptist prepared people for the ministry of Jesus Christ, whom the Bible says is the savior of the world. John urged people to take their spiritual growth seriously by repenting of (turning away from) their sins. Verse 11 records John saying: "I baptize you with water for repentance. But after me comes one who is more powerful than I, whose sandals I am not worthy to carry. He will baptize you with the Holy Spirit and fire."
Fulfilling God's Plan
Matthew 3:13-15 records: "Then Jesus came from Galilee to the Jordan to be baptized by John. But John tried to deter him, saying, 'I need to be baptized by you, and do you come to me?'
Jesus replied, 'Let it be so now; it is proper for us to do this to fulfill all righteousness.' Then John consented."
Although Jesus didn't have any sins to wash away (the Bible says he was completely holy, since he was God incarnated as a person), Jesus here tells John that it is nevertheless God's will for him to be baptized "to fulfill all righteousness." Jesus was fulfilling the baptism law that God had established in the Torah (the Bible's Old Testament) and symbolically portraying his role as the world's savior (who would spiritually purify people of their sins) as a sign to people of his identity before he began his public ministry on Earth.
The story continues in Matthew 3:16-17: "As soon as Jesus was baptized, he went up out of the water. At that moment heaven was opened, and he saw the Spirit of God descending like a dove and alighting on him. And a voice from heaven said, 'This is my Son, whom I love; with him I am well pleased.'"
This miraculous moment shows all three parts of the Christian Trinity (the three unified parts of God) in action: God the Father (the voice speaking from heaven), Jesus the Son (the person rising up out of the water), and the Holy Spirit (the dove). It demonstrates the loving unity between the three distinct aspects of God.
The dove symbolizes peace between God and human beings, going back to the time when Noah sent a dove out of his ark to see if the water that God had used to flood the Earth (to destroy sinful people) had receded. The dove brought back an olive leaf, showing Noah that dry land suitable for life to flourish again had appeared on Earth. Ever since the dove brought back the good news that God's wrath (expressed through the flood) was giving way to peace between him and sinful humanity, the dove has been a symbol of peace. Here, the Holy Spirit appears as a dove at Jesus' baptism to show that, through Jesus, God would pay the price that justice requires for sin so humanity could enjoy ultimate peace with God.
John Testifies about Jesus
The Bible's Gospel of John (which was written by another John: the Apostle John, one of Jesus' original 12 disciples), records what John the Baptist later said about the experience of seeing the Holy Spirit miraculously come to rest on Jesus. In John 1:29-34, John the Baptist describes how that miracle confirmed Jesus' true identity as the savior "who takes away the sin of the world" (verse 29) to him.
Verse 32-34 record John the Baptist saying: "I saw the Spirit come down from heaven as a dove and remain on him. And I myself did not know him, but the one who sent me to baptize with water told me, 'The man on whom you see the Spirit come down and remain is the one who will baptize with the Holy Spirit.' I have seen and I testify that this is God’s Chosen One."