Now the people were filled with expectation, and all were asking in their hearts whether John might be the Messiah. John answered them all, saying, "I am baptizing you with water, but one mightier than I is coming. I am not worthy to loosen the thongs of his sandals. He will baptize you with the Holy Spirit and fire. 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."
"Now the people were filled with expectation, and all were asking in their hearts whether John might be the Messiah." (cf. verse 15)
At the beginning of today's Gospel, we see the people full of expectation "whether John might not himself be the Messiah." We have already considered this passage on the 3rd Sunday of Advent. The Baptist's preaching and the question of the Messiah obviously move many people in Israel, for the times under Herod are so bad that the whole people are in expectation of a redeeming Messiah.
John answered them all, saying, "I am baptizing you with water, but one mightier than I is coming. I am not worthy to loosen the thongs of his sandals. He will baptize you with the Holy Spirit and fire." (cf. verse 16)
John takes up this expectation of the Messiah and answers the waiting people with a promise of salvation. He speaks of a baptism of fire and a saving baptism in the Holy Spirit. John himself contrasts his baptism in water with the baptism in the Spirit and the baptism in fire of the One who is to come. His message of salvation is thus both an admonition and a warning, for, in the baptism of fire, there is purification and possibly even judgement of those who do not accept the baptism of the Spirit.
So, John announces this one stronger, and for the listeners, it must obviously have been clear who is meant by this. Therefore, this stronger one is a person who is already known, who is already in their midst, as John puts it: He is already among you, but you do not know him. The loosening of the sandals indicates that the Baptist, as a herald, totally submits to Christ, more so than a slave. A slave laces his master's sandals, but John says: I am not even worthy to do this.
When John says that he baptises only with water, this is a promise that the baptism of the stronger one, the one who comes after him, that is, Jesus Christ, will wash away sins and at the same time also communicate the Holy Spirit. The expression "he will baptise in the Holy Spirit and in fire" therefore means: whoever is not baptised with the Holy Spirit or does not allow himself to be baptised will be destroyed in the fire. The baptism of fire is reminiscent of the judgement that will come to those who do not accept the baptism of the Spirit, the baptism in the Holy Spirit, i.e., the decision for Christ. After the exile, the Jewish people waited with the greatest longing for this communication of the Spirit.
"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." (cf. verse 21-22)
The baptismal account that now follows is to be interpreted in two ways. Firstly, Jesus is confirmed as the Son of God, and secondly, this baptism is the anointing as the Messiah. Before, John spoke of the stronger one who would come. Now, this stronger one is made manifest by God himself before all the people.
What then happens is described in three infinitives, that is, simple statements: Heaven opens, the Holy Spirit descends on Jesus, and the voice of the Father speaks from heaven. These three infinitives are ordered in such a way that the first makes the other two possible. Heaven opens above Jesus, and therefore the following can now happen. Then, out of the opened heaven, the Holy Spirit comes for all to see, and the voice of God comes for all to hear.
So, God reveals himself and speaks to his people again. He has not done this since the exile, since the exile of the last hundred years. There were no more prophets. That is why the people’s longing for the Messiah, for the sending of the Spirit and for God to speak to them again is so great. And that is precisely what happens here: While Jesus prays, heaven opens, i.e., in response to Jesus' prayer, God has again begun to reveal himself to people. In the baptism of Jesus, God himself reveals the Son and presents Jesus to all Israel, for all see the Spirit and hear the voice. Now the prophetic words of the Holy Scriptures, the words of the archangel Gabriel to Mary and the words of the angels to the shepherds at the birth in Bethlehem become firm certainty, witnessed by the Father through the Holy Spirit, visible and audible to all.
The fact that John as the baptiser is no longer mentioned here at all is a sign of his self-assessment. This being ignored is the consequence of John's deep, humble attitude, who still places himself among the slaves and says of himself: "I am not even worthy to untie the laces of Jesus' shoes.
At the baptism of Jesus, the baptism of the Spirit, which promised the baptism of water, becomes reality, but for the time being only with Jesus. God only addresses Jesus, although all who are there are baptised. All are now listeners and experience in Jesus from the Father what is also promised to them. The phrase "the Spirit descended" and the definite article "the Spirit" point to a person. Therefore, the Holy Spirit is not merely a quality of God, but a person: You, Christ, are the one announced by John who will baptise with the Holy Spirit.
In the baptismal event of Jesus, the post-Easter sequence is already given and indicated, as it happens after redemption until today: Jesus is baptised, comes out of the Jordan and prays. Then the anointing with the Holy Spirit takes place. This is also the ecclesiastical order until today: first baptism, then confirmation. Now Jesus is confirmed as the Son of God.
In the following verses following this Gospel, Jesus' family tree is enumerated, and his age is mentioned. These are necessary additions, for the Messiah comes from the tribe of David. He is not merely a spirit coming from heaven but truly human. He is fully the Son of God and fully the Son of Man. This is the basic prerequisite for his whole proclamation and for salvation. That is why this reality is described very clearly here by Luke. ∎