Q: Is water baptism necessary for salvation in Christ?

A: To answer this, let's look at an article by Robert Gromacki, entitled Repent and Be Baptized.
On the Day of Pentecost, Peter stood before a large crowd of Jews and declared: "Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Spirit" (Acts 2:38). A reader has indicated that this verse has caused much confusion and seems to imply that water baptism is required for salvation.
There is a great difference between the real, intended meaning of a verse and its implied meaning. Implied understanding is based upon the first reading of a passage, but the correct interpretation can be gained only through a serious study of the verse itself, its context, and its relationship to the clear teaching of Scripture found elsewhere.
Several church groups believe in baptismal regeneration; teaching that both repentant faith and water baptism are essential prerequisites to personal salvation. To such groups, one must be baptized in water for the express purpose of gaining the remission of sins. A person thus expresses his faith in and through the necessary baptismal rite, not apart from it. These groups definitely point to Acts 2:38 as one of their supporting passages.
Our reader has asked for an answer to the claim of these groups. By following five steps, we can show that this verse does not teach that water baptism is essential to personal salvation.
Grammar
The grammar of the verse indicates that only repentance is required to receive the remission of sins. Here is my translation of the verse from the Greek, using some extra words to bring out some key differences not observable in the English text: "Repent [you, plural], and let each one [singular] of you be baptized [singular], upon the name of Jesus Christ into the remission of sins, and you will receive [you, plural] the gift of the Holy Spirit."
The command to repent and the promise to receive are both plural verbs. The command to be baptized is singular. The imperative ("let each one of you be baptized") is parenthetical. Peter's actual command was: "Repent . . . upon the name of Jesus Christ into the remission of sins, and ye shall receive the gift of the Holy Spirit." Peter gave the audience only one thing to do in order to receive the remission of sins. There was only one direct command: "Repent [you, plural]."
Some other commentators approach the verse in a different way. They focus on the word "for" in the phrase "for the remission of sins." This word is a preposition (eis in Greek), normally translated as "into." But it can also be translated as "because of" or "on the basis of." In Matthew 12:41, Christ stated that the men of Nineveh "repented at the preaching of Jonah." The word "at" is the preposition eis, translated as "for" in Acts 2:38. Obviously the men of Nineveh did not repent to get the preaching of Jonah. Rather, they repented because Jonah had preached. The preaching occurred before the repentance. Likewise, the remission of sins in Acts 2:38 happened before the practice of water baptism.
Both of these views present acceptable alternatives to the view of baptismal regeneration.
Immediate Context
Second, the immediate context of the verse shows that only repentant faith is needed to gain divine forgiveness. Earlier in his message, Peter quoted from Joel (Acts 2:16-20) and concluded with that Old Testament prophet's evangelistic appeal: "And it shall come to pass, that whosoever shall call on the name of the Lord shall be saved" (v. 21). In the Old Testament period, people became saved by calling upon Jehovah-God. They acknowledged their sinful need, believed that only God could deliver them, and placed their trust in Him. They did not submit to water baptism. If Peter meant that baptism was essential to salvation, then why did he quote from Joel? The reference would be irrelevant.
Later, Peter demonstrated that Jesus Christ was the One, the Lord-God, upon whom his audience should call in repentant faith. God the Father authenticated Christ through His miracles, death, resurrection and ascension into heaven (vv. 22-35). Peter then said: "Therefore let the house of Israel know assuredly, that God hath made that same Jesus, whom ye have crucified, both Lord and Christ" (v. 36).
The context later states: "Then they that gladly received his word were baptized" (v. 41). What was the word they received? It was the content of Peter's sermon in which he demonstrated the deity and messiahship of Jesus Christ and the necessity to call upon Him for salvation. When they called upon Christ, they repented. That act of faith brought the remission of sins. They were then individually baptized to show their new identification with Christ.
Greater Context
Third, the greater context of the Book of Acts reveals that only repentant faith is the basis of securing divine forgiveness. Later, in his sermon at Solomon's Porch within the Temple, Peter appealed to the crowd; "Repent ye therefore, and be converted, that your sins may be blotted out" (Acts 3:19). There is no mention of water baptism here as a requirement for the removal of sins.
When Peter stood before the unsaved religious leaders who had just imprisoned the apostles, he proclaimed: "The God of our fathers raised up Jesus, whom ye slew and hanged on a tree. Him hath God exalted with his right hand to be a Prince and a Savior, for to give repentance to Israel, and forgiveness of sins" (5:30,31). Please note that repentance and forgiveness are joined. The human cause of salvation is repentance, and the divine effect is forgiveness.
When Peter explained the Gospel to the family of Cornelius, he stated: "To him [Christ] give all the prophets witness, that through his name whosoever believeth in him shall receive remission of sins" (10:43). That verse is extremely clear and simple. And the same person who spoke Acts 2:38 spoke Acts 10:43. Peter, thus, is his own best interpreter. When Cornelius' family heard those gracious words, they believed, received divine forgiveness, and were filled with the Holy Spirit (v. 44). These divine blessings came as a result of a faith-only experience. Although Cornelius and his house were baptized later, they were not baptized to receive the remission of sins. They already had that spiritual reality.
Later Peter explained to the Christians at Jerusalem the operation of God and the conversion of Cornelius and his family. They responded by glorifying God and saying: "Then hath God also to the Gentiles granted repentance unto life" (11:18).
Paul definitely indicated that water baptism plays no part in the securing of redemption. He exclaimed at Antioch in Pisidia: "Be it known unto you therefore, men and brethren, that through this man is preached unto you the forgiveness of sins: And by him all that believe are justified from all things" (13:38,39). Add to that declaration the truth that Paul wrote to the Corinthians: "For Christ sent me not to baptize, but to preach the gospel" (1 Cor. 1:17). Please note the juxtaposition between baptism and the Gospel message. Baptism is not an essential part of the Gospel. Submission to water baptism is a requirement for obedience after salvation (Matt. 28:18-20), but it is not a prerequisite to spiritual regeneration.
Ministry of John the Baptist
Fourth, Peter's statement in Acts 2:38 can be interpreted in the light of the ministry of John the Baptist. The forerunner of Christ preached: "Repent ye: for the kingdom of heaven is at hand" (Matt. 3:2). Mark wrote that John proclaimed "the baptism of repentance for the remission of sins" (Mark 1:4). Three features are common between this verse and Peter's appeal: baptism, repentance and remission of sins. But what actually secures the remission of sins? It is the repentance that produces the divine forgiveness. Water baptism is simply the outward sign or mode through which the believing sinner confesses the fact that he has already been forgiven through repentant faith in the saving Person and work of Christ.
Doctrine of Salvation
Fifth, the doctrine of salvation, taught throughout all of the Scriptures and evidenced in all dispensations and ages, stresses that only repentant faith is necessary to be justified and to receive divine forgiveness. Abraham "believed in the Lord; and [God] counted it to him for righteousness" (Gen. 15:6). From one age to another, the means of getting saved has remained the same. That is why New Testament writers often refer to Old Testament characters as examples of faith. To teach that water baptism is essential to salvation in this Church Age is to say that God has changed the method to gain justification.
Dear readers, rejoice in the truth: "For by grace are ye saved through faith; and that not of yourselves: it is the gift of God" (Eph. 2:8).