“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." (Luke3:21-22)
Pope Benedict commented on this passage from the Gospel of Luke in his homily for the Feast of the Baptism of the Lord in 2010:
“As soon as he sees Jesus approaching, John realizes that there is something unique in this Man, that he is the mysterious Other for whom he has been waiting and to whom his whole life is oriented. He understands that before him stands One who is greater than he, the thong of whose sandals he is not even worthy to untie.
At the Jordan Jesus reveals himself with an extraordinary humility, reminiscent of the poverty and simplicity of the Child laid in the manger, and anticipates the sentiments with which, at the end of his days on earth, he will come to the point of washing the feet of the disciples and suffering the terrible humiliation of the Cross. The Son of God, the One who is without sin, puts himself among sinners, demonstrates God's closeness to the process of the human being's conversion. Jesus takes upon his shoulders the burden of sin of the whole of humanity, he begins his mission by putting himself in our place, in the place of sinners, in the perspective of the Cross.
While absorbed in prayer he emerges from the water after his Baptism, the skies break open. It is the moment awaited by so many prophets: "O that you would rend the heavens and come down!" Isaiah had prayed (64: 1). At that moment, St Luke seems to suggest, this prayer is heard. Indeed, "The heaven was opened, and the Holy Spirit descended upon him" (3: 21-22); and words were heard that had never been heard before: "You are my beloved Son; with you I am well pleased" (v. 22).”
In this particular passage, we can see the anointing of the Lord Jesus. The Holy Spirit, the Breath of God present from the beginning of time (Genesis 1:2), the Spirit that made life possible, had been sent down upon the God-Man Jesus in this perfect act of submission to the will of the Father for the salvation of all! God, in His wisdom, realizes that we are human beings, we learn through our senses and through experience. How best, then, to teach us about the unseen spiritual world than by exhibiting in His own incarnate life the effects of this spiritual anointing? It is by revealing the work of the Holy Spirit, the anointing that is far beyond that of Moses when, instructed by God Himself, he anointed the sacred things to be used in the worship of the God of Abraham Isaac and Jacob. He used olive oil, that pure oil that the Church requires for all the holy oils, and he anointed the sacred vessels, the altars and the vestments of the priests. He anointed his brother Aaron to be the first High Priest of God in Israel with the same oil. It was a visible and tangible manifestation of the holy anointing of God’s Spirit that descended and made holy all that was dedicated to the Lord.
In the same way, the prophet Samuel, sent by God to the House of Jesse, anointed the Lord’s choice King of Israel. After having rejected all of the elder sons of Jesse, the youngest was called in from the sheepfolds and it was this son, David, who was anointed with the holy oil to be the King of Israel.
Jesus, after submitting Himself to the baptism of John as a way to consecrate the life-giving waters of baptism for those of us who would follow, was then anointed by the Holy Spirit, a confirmation of the Lord’s identity as God and Son of God, as well as a “visible sign of an invisible reality,” the definition of a sacrament. The Catechism teaches us about this sacred anointing and confirmation of the role of Jesus and His identity:
438 Jesus' messianic consecration reveals his divine mission, "for the name 'Christ' implies 'he who anointed', 'he who was anointed' and 'the very anointing with which he was anointed'. The one who anointed is the Father, the one who was anointed is the Son, and he was anointed with the Spirit who is the anointing.'"(St. Irenaeus) His eternal messianic consecration was revealed during the time of his earthly life at the moment of his baptism by John, when "God anointed Jesus of Nazareth with the Holy Spirit and with power", "that he might be revealed to Israel" (Acts 10:38; Jn 1:31) as its Messiah. His works and words will manifest him as "the Holy One of God". (Mk 1:24; Jn 6:69; Acts 3:14)