The following is an excerpt from article DB040 from the Christian Research Journal by Hank Hanegraaff. You can view the PDF of the full article by clicking on the link below the excerpt.
The most critical mistake one can make with regard to baptism is to believe that it is necessary for salvation. Several aberrant or cultic movements, such as the International Churches of Christ (Boston movement), teach that belief is not sufficient for salvation — baptism is also required. In concert with other cultic groups, they distort passages such as Acts 2:38 to defend this deadly doctrine.
Acts 2:38 climaxes Peter’s powerful proclamation of the gospel on the day of Pentecost. Those impacted by his message cried out, “What shall we do?” Peter replied, “Repent and be baptized, every one of you, in the name of Jesus Christ so that your sins may be forgiven. And you will receive the gift of the Holy Spirit.”
Groups that believe baptism is necessary for salvation mistakenly regard Peter’s words, “Repent and be baptized” as evidence that belief plus baptism results in salvation. Scripture, however, does not support this view.
First, the Book of Acts itself demonstrates that baptism is the sign of conversion, not the means of conversion. Acts 10:47, for example, describes believers who were indwelt by the Holy Spirit (and therefore saved — see Rom. 8:9) prior to being baptized.
Furthermore, the Bible as a whole clearly communicates that we are saved by faith and not by works (Eph. 2:8-9). As Paul pointed out in Romans, our righteous standing before God is “by faith from first to last” (Rom. 1:17). When the jailer asked the apostle Paul, “What must I do to be saved?” Paul responded, “Believe in the Lord Jesus, and you will be saved” (Acts 16:30-31).
Although baptism is not the means by which we are saved, it is the means by which we are set apart. By baptism, we testify that we are no longer our own — we have been bought by Christ’s blood and have been brought into the community of faith. This is the significance of Peters command in Acts 2:38. He was not telling them that they could not be saved without baptism. He was telling them that their genuine repentance, which by the grace of God accompanies salvation, would be evidenced by their baptism.