Today we celebrate the feast of the Baptism of the Lord. In today's Gospel, as in the other Gospel accounts of Jesus' baptism, we hear John the Baptist address the confusion of the people who thought that John might be the Messiah. In response, John contrasts the baptism that he performs with the Baptism that Jesus will inaugurate. John the Baptist says that he has baptized with water, but that someone will come and baptize with the Holy Spirit. The type of baptism that John performed was not yet a Christian Baptism; it was a preparation for Christian Baptism through which sins are forgiven and the gift of the Holy Spirit is received.
The baptism of Jesus is reported in each of the three Synoptic Gospels—Matthew, Mark, and Luke. Clearly, it was an event of great significance for Jesus and for the early Christian community. The Evangelists Mark and Luke report the story from Jesus' perspective; the voice from heaven is addressed to Jesus. Compare this to Matthew's Gospel in which the voice from heaven speaks to everyone. In Luke, however, the Holy Spirit descends upon Jesus during his time of prayer after his baptism. Through his Gospel, Luke will show Jesus to be a person of prayer who withdraws regularly from the crowds and his disciples to pray to his Father.
The baptism of Jesus is considered a manifestation of God in Jesus, another “epiphany.” On this, the last day of the Christmas season, our Gospel reveals to us Jesus' relation to God: the son of Mary and Joseph is also God's own Son. In Luke's Gospel, all three members of the Trinity are manifested here: God the Father in the voice, the Holy Spirit descending, and Jesus the Son. At the beginning of his Gospel, Luke is communicating to us important information about the identity of Jesus. In the verses that follow, Luke lists the genealogy of Jesus, tracing Jesus' ancestry back to the first person, Adam, who is also identified as the son of God. We, the children of Adam and Eve, are again made children of God through Baptism.(Loyola Press, Sunday Connection)