The Baptism of Jesus
9 At that time Jesus came from Nazareth in Galilee and was baptized by John in the Jordan. 10 Just as Jesus was coming up out of the water, he saw heaven being torn open and the Spirit descending on him like a dove. 11 And a voice came from heaven: “You are my Son, whom I love; with you I am well pleased.”
12 At once the Spirit sent him out into the wilderness, 13 and he was in the wilderness forty days, being tempted[a] by Satan. He was with the wild animals, and angels attended him.
14 After John was put in prison, Jesus went into Galilee, proclaiming the good news of God. 15 “The time has come,” he said. “The kingdom of God has come near. Repent and believe the good news!”
Why was Christ the Lord baptized?
Saint John Chrysostom, Homilies, homily at Matthew, homily X, II, in Church fathers and writers(1994), vol. 23, pp. 122-123
As it was not possible that John, by taking Christ by hand, to go from house to house and tell them: Believe in this one! but it had to happen in front of everyone to be heard that blessed voice from heaven and to take place all the rest. For this reason Jesus came to be baptized. The fame of John the Baptist and the novelty of the event drew attention and called all Jerusalim at Jordan. The shores of Jordan became a grand scene. Those who came there were made by John the Baptist to humble themselves, being convinced by him they were not so grand; he showed them they were guilty of the greatest sins and they could welcome the One who was to come if they repented, leaving their ancestors aside and not boasting about them. The life of Christ was not known yet and it was believed he was killed together with the other infants from Betlehem. Even if He appeared in the world when He was twelve He became again unnoticed. That is why his appearance in the world had to take place in such a wonderful way, to have a great beginning. That is why then on the shores of Jordan the Jews heard what they had not heard from the prophets or from others. John the Baptist was preaching with an impressive voice, reminding them of heaven and of the Kingdom from above, not telling them anything about the land.
Saint John Chrysostom, Homilies at Matthew, homily XII, I, in Church Fathers and writers (1994), vol. 23, p. 145
`And for not thinking anything wrong when seeing Him coming to be baptized, John the Baptist stops Him by saying: I need to be baptized by you, and do you come to me? (Matthew 3, 14)
As the baptism performed by John the Baptist was one of repentance which made the people condemn their own sins and in order not to think that Christ had come with such a thought in mind at Jordan, John the Baptist warns you by calling Him Lamb and Redeemer of all sins of the world. It goes without saying that the One Who can take away the sins of the whole human race is without sin.
For this reason John did not say : See the One without sin ! but something more: Look the lamb of God who takes away the sin of the world (John 1,29) to receive with complete trust both facts: that He is without sin and that He takes away the sin of the world – and when you have received this to understand that He came to baptism to settle other things.`