There are churches which use Acts 2:38 to build an entire case that baptism is required for salvation. It says, "Peter said to them, ‘Repent, and each of you be baptized in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the Holy Spirit.’" If we knew nothing about the rest of the New Testament, we might read this verse and think that it is repentance and baptism which are necessary for forgiveness. We might think also that baptism is required in order to receive the Holy Spirit. Neither of these beliefs, however, are taught in the rest of the Bible.
The message of grace alone and faith alone is clear in the Scripture. Ephesians 2:8-9 says, "For by grace you have been saved through faith; and that not of yourselves, it is the gift of God; not as a result of works, so that no one may boast." The message here is clear that we are saved by faith in Christ, not by any works that we could do. There are Christian traditions that teach that grace is imparted to us as we do good works. These say that good works such as baptism or communion become the means of grace through which righteousness is granted us. Thus, we end up earning the grace of God through righteous deeds, and faith becomes a work. A gift is not a gift if we labor for it. It must be free. Romans 6:23 says, "For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord." Salvation is not by works but by faith. Believing the gospel and surrendering our hearts willingly to Christ is our hope of salvation, not that somehow holiness can come to us as we do some religious acts.
Romans 3:28 says, "For we maintain that a man is justified by faith apart from works of the Law." And Galatians 2:16 says, "Nevertheless knowing that a man is not justified by the works of the Law but through faith in Christ Jesus, even we have believed in Christ Jesus, so that we may be justified by faith in Christ and not by the works of the Law; since by the works of the Law no flesh will be justified." In other words, the only "work" that man can do to receive the favor of God through grace in Christ is to believe. Our belief in the truth about Christ causes us to repent of our sins and surrender to Him as Savior and Lord. As Jesus said in John 6:29, "Jesus answered and said to them, ‘This is the work of God, that you believe in Him whom He has sent.’" The clear Biblical truth is that we are justified by faith, not by works, and salvation is ultimately a work of God, not of man. Works follow as a result of saving faith, but we cannot be made righteous by doing good. Why? Because we are born with a sin nature and are unable to please God (Romans 5:12).
Based on this, we know first and foremost that baptism is not something that can save us, or we will contradict all the verses we have already mentioned. Some try to get around this by saying that baptism is not a work, but then I must ask "What is?" The bottom line is that merely being immersed in water doesn’t save anybody. The issue is the sin of the heart, not the dirt of the body. God has always been interested in clean hearts (Psalm 24:4, 51:10). 1 Peter 3:21 makes this abundantly clear saying, "Corresponding to that, baptism now saves you-- not the removal of dirt from the flesh, but an appeal to God for a good conscience--through the resurrection of Jesus Christ." Does water baptism save us? Peter says "no." Asking God to forgive us of our sins by faith does. This is the type of spiritual "baptism" that Peter says we need, not merely a washing away of dirt from our skin. It is our hearts that need to be cleansed from the filth of sin. This baptism of the heart through the resurrection of Christ (see Romans 6:4) is what salvation is all about as we become immersed in Christ by faith, trusting in His work on the cross and subsequent resurrection to be our means to holiness and to heaven. Only through faith can our hearts be cleansed. Water baptism then follows. The clearest example is perhaps Acts 10:43-48 in which some receive the Holy Spirit but do not get baptized until a later date. Peter doesn’t suppose that they aren’t saved but that they just hadn’t had a chance to express publicly their devotion to Christ and to be visibly and tangibly welcomed into the family of God through water baptism. Water baptism is a visual manifestation and testimony to a spiritual baptism that has already occurred by faith.
There is plenty more evidence still. If baptism saves us, then Jesus Himself wasn’t even saved before His baptism at age 30. The thief on the cross who repented was never baptized, but Christ promised that He would arrive in paradise. To merely discount these examples as "exceptions" is to be unfair to the full counsel of Scripture. Clearly, the thief was saved because it was his faith that justified him, just as it did Abraham and all who have believed since. Romans 4:2-3 says, "For if Abraham was justified by works, he has something to boast about, but not before God. For what does the Scripture say? ‘ABRAHAM BELIEVED GOD, AND IT WAS CREDITED TO HIM AS RIGHTEOUSNESS.’" Neither baptism nor circumcision resulted in salvation for Abraham, but it was his faith. The same is true for us today.
Taking the whole account of Scripture, it is clear that salvation is by faith alone, not by any works, water baptism included. Water baptism is important, but we must understand its proper purpose.