The normative declaration of one's choosing to enter into discipleship is baptism, but the question remains as to whether Luke saw the water ceremony itself as salvific. Indeed, most who believe in baptismal regeneration will quote 2:38, "repent and be baptized for the forgiveness or sins." Some have attempted to argue that the preposition eis here means "in view of," but this is not really the normative use of the preposition that typically conveys the idea of leading to a goal. Hence, a more correct translation would be, "leading to the forgiveness of sins," or "with the goal of having one's sins forgiven."
The question, instead, is whether baptism, i.e., the initiation ritual, is being used in a literal way that refers to the act of the water ceremony as that which is leading to forgiveness, or whether the water ceremony, since it is the public declaration of one's faith, is being used in a representational manner, as putting on a ring in a wedding ceremony can represent the act of getting married and causing marriage, even though the ring, a mere symbol within itself, does not marry anyone or necessarily lead to marriage.
In order to answer this question in Luke, two trajectories of questioning can be pursued. The first is whether forgiveness of sins and the reception of the gift of the Holy Spirit is given before, during, or after one is baptized, displaying that it is not the water ceremony itself that does anything, but rather the repentance and faith allegiance to Christ through apostolic teaching that is the means for the forgiveness of sins in distinction from the water ceremony, even though the timing of the event can coincide with the giving of the gift.
The second line of questioning may come from the preaching of the gospel message itself. What is Luke's understanding of how one should respond to the gospel message, and does he use the term "baptism" interchangeably with other terminology that refers to the faith allegiance one makes, so as to show that when he uses the term "baptism," he is using it as a synecdoche, something associated with a larger whole that can represent the larger whole, like the wedding ring can represent one's wedding in the phrase, "He put a ring on it," meaning "he married her."
The Argument from the Spirit's Indwelling
To answer the first question, we see Luke presenting believers as receiving the Holy Spirit
In 8:12-18, Luke presents converts who were baptized as not yet receiving the Holy Spirit, but only doing so after the apostles go to lay hands on them, a possible indication by Luke that submission to the apostolic teaching is required when one transfers his allegiance to Jesus Christ as Lord (without which the Holy Spirit is not given). Philip had already given the word necessary to accompany baptism, yet this submission to the apostolic authority seemed an additional necessity.
Again, in 19:1-6, Luke presents Paul as stating that there are believers who have only been baptized by the baptism of John, a baptism of repentance that was only half complete. As Paul argued, it looked forward to Christ, so that it called people away from sins, but was a baptism waiting for the Messiah. After laying hands on them, they receive the Holy Spirit that they did not receive in either a belief in John's teaching or in the water ceremony (neither in John's baptism nor by being baptized in Jesus' name this time).
I suppose one could argue that the specific circumstances in 19 are different than those in 8, as the full gospel message is not communicated. The problem is that once it is communicated and they are baptized. they still do not receive the Spirit until Paul lays hands upon them, displaying that baptism was not the cause of their receiving the Holy Spirit, which they previously said they did not receive or even know about.
Conversely, in 10:42-48, the Holy Spirit comes upon them while Peter is still preaching the gospel message that "everyone who believes in Him receives forgiveness of sins through His name." Peter, as a result, argues that they should be baptized (make the public declaration), since God has given the Holy Spirit to them. If they are given the Spirit already, what is the purpose of the baptism that is somehow meant to regenerate in the giving of the Spirit?
Luke, clearly, does not see the water as having any regenerative power, even when joined to the word. If he did, why would he present baptism as ineffectual in its ability to give the Holy Spirit to believers, as in Chapters 8 and 19? And why does he present baptism as something that those who have believed and received the Holy Spirit already do not need it to receive the Holy Spirit and faith, but somehow it is important to do it anyway?
Baptism, to Luke, seems to be what baptism is in Second Temple Judaism and the Bible in general. Luke isn't making up some special definition for it. It is a public declaration of one's faith allegiance to Christ, that one is becoming his disciple. The gift of faith and regeneration can precede, be concomitant with, or follow the initiation rite, and in fact, no regeneration can occur with all of these present (as is implied by the case of Simon in 8:13, 18-24).
In fact, Luke gives his view of true baptism as that which is the giving of the Holy Spirit, which is contrasted with water at the beginning of the book. In 1:5, Jesus repeats what John states in the Gospels:
"For John baptized with water, but you will be baptized with the Holy Spirit not many days from now.”
In fact, the 11 apostles, along with the other 109 disciples, are actually never said to be baptized by water in the name of Christ. A couple of them were disciples of John and were baptized by him, but we see in Acts 19 that this baptism is invalid. Hence, Paul has to baptize those who only have the baptism of John again. Instead, the greater baptism seems to be that which the water reflects, i.e., a spiritual washing of an individual who is being placed into God's kingdom. Hence, the baptism of the Holy Spirit seems sufficient for the apostles, and they have no need to be baptized themselves. Only Paul, who did not receive the Spirit at Pentecost with them, is baptized with water. Even here, however, Paul seems to receive the Spirit and salvation into the body of Christ before he is baptized. Ananias calls him a "brother," which may be explained away as an expression for a fellow Jew, even though it could also refer to their newfound Christian relationship, but he also tells him that he has come so that he may be filled with the Holy Spirit, and when he lays hands on him, his blindness is taken away, a perfect image for regeneration. Only after this does he submit to the water ceremony.
The Argument from Synonyms
The second trajectory in seeking Luke's view of baptism is that of analyzing his recordings of the presentations of the gospel. If "baptism" is used in place of other words within the presentation, and other words are in place of one another, then we can see that he is using these terms interchangeably for one another, and not referring to something in addition to it.
Luke's most commonly presented gospel message calls upon people to "believe," and shows them responding to the gospel by believing. The reader is told that people are called to "believe on the Lord Jesus Christ," "believe in His Son," etc. Many times they are told to "repent." Sometimes the people are said to believe and are baptized, and sometimes baptism becomes a part of that message, as in 2:38. All of this seems to be mixed in together as referring to the same thing, which is a transfer of allegiance from one's sins, false religion, etc. to God by receiving His Messiah.
But there is only a single mention of the gospel being preached as "repent and be baptized" (2:38). The imperative command, "Be baptized" takes its place where normally the imperative "believe" (or one of its synonyms) would be.
In 22:16, Christ tells Paul to "be baptized and have your sins washed away, calling upon His name." Baptism here is the act where Paul is told to call upon His name. In other words, it is identified as the act of repentance and commitment to God.
Likewise, in 3:19, the phrase, "turn to God" replaces both the imperatives "be baptized" and "believe."
“Repent, then, and turn to God, so that your sins may be wiped out, that times of refreshing may come from the Lord."
In the book of Acts, we see various phrases used in parallel to one another, indicating that Luke is attempting to say something about the nature of faith. Again, in 26:20, Paul states, “but I declared to those in Damascus first, and then to those in Jerusalem and in all Judea, and to the Gentiles, that they should repent and turn to God, performing deeds consistent with repentance.”
Here we have the phrase, “repent and turn to God.” This describes the transference of allegiance that we are being commanded to make.
In 11:21, those who come to believe are also said to "turn to God."
Paul summarizes the message of the gospel, his mission to talk about it, and all of these various ways of describing it, giving us the biblical definition of faith in Acts 20:21, “testifying to both Jews and Greeks about repentance toward God and faith in our Lord Jesus.”
In Acts 17:30, Paul just says the word “repent” because the word itself can encapsulate the idea of transferring one’s allegiance. Hence, both the message of John the Baptist and Jesus are summarized as, “Repent for the kingdom of God is here,” even though one can just mean repentance from something and the other repentance both from and to something (i.e., a turning away versus a turning away and toward something).
At other times, the term “believe,” since in the NT this refers to giving one’s allegiance to someone (e.g., the soldiers in Caesar’s army were told to believe on/have their faith in him, meaning to give their allegiance to him) can replace the additional need to mention repentance, as giving one's primary allegiance to another implies the taking of it away from a previous allegiance to which one was committed.
13:39 states that “everyone who believes is justified.”
“About him all the prophets testify, that everyone who believes in him receives forgiveness of sins through his name” (10:43).
Then he brought them outside and asked, “Sirs, what must I do to be saved?” They replied, “Believe on the Lord Jesus and you will be saved, you and your household.” Then they spoke the word of the Lord to him, along with all those who were in his house. At that hour of the night he took them and washed their wounds; then he and all his family were baptized right away” (16:30-33).
Here we see the tie into baptism. It was usually done right away as someone publicly declared their new allegiance to a person or group and their teachings. Since baptism is the ceremony where one declares this transference of allegiance publicly, the word and concept of washing is often used as a synecdoche, referring to the person’s transfer of allegiance, not necessarily the literal water ceremony. This is also why the imagery is often used when referring to the Holy Spirit washing someone in a spiritual regeneration, rather than referring to literal water (Mark 1:8; Matt 3:11; Titus 3:5—the washing here is described as the washing of regeneration/rebirth done by the Holy Spirit, not a washing of literal water).
This is why we see people believing and receiving the Holy Spirit before they are baptized, because baptism is the water ceremony, not the event through which one receives the Holy Spirit and is regenerated, which is the faith in the apostolic message that occurs many times before the water ceremony, and a couple times, after it.
Hence, it is faith that saves, not the baptism ceremony. These simply are common practices that accompany one’s faith allegiance, and so they often represent that transfer of allegiance itself.
So this transference of allegiance is described as "turning to God," “being baptized,” just “repenting,” or just “believing,” or a combination of them in the book of Acts. These are all synonymous for the same event where one transfers his allegiance to Christ as Lord. One hears and does what is commanded, which is to repent and believe on the Lord Jesus Christ, to have faith, to transfer one’s allegiance to Christ, to turn to God away from one's self allegiance or allegiance to another god or religion.
What this means is that Luke's view of baptism is that the water ceremony is symbolic of one's faith commitment to submit to the Person of Christ, His work, and His teachings and that come to us via the apostles. One normally enters the Christian life declaring his commitment by being baptized by an authorized individual of the community. But one cannot call himself a Christian without this faith commitment, even if he has believed the gospel message is true and was baptized (as in the case of Simon the magician), or went through a water ceremony where the individual does not dedicate himself to the teachings of the Lord Jesus Christ and His apostles in order to become a convert (as in the case of those baptized with John's baptism). The gift of the Holy Spirit can be received without it completely (as is the case with the 11 apostles), before one receives it, or after one receives it, thus showing that the ceremony is not the cause of the receiving of the Spirit, but the faith commitment to Christ and His teaching.
When Luke, therefore, uses the imperative command "be baptized" in place of the imperatival commands like "believe," or "turn to God," he is merely using it in a representational way that refers to the same thing that those other terms do.