Is baptism purely symbolic, or is baptism necessary for regeneration?
Baptism is not necessary for salvation, but that doesn’t mean that baptism is purely symbolic. In the early church, if there were alter calls, they would have included baptism. Baptism is more than symbolic. It’s a statement that is made that involves grace that God provides.
However, is being baptized a prerequisite for regeneration? The direct answer is, "no." I understand Peter’s first sermon in Acts 2 ("...for the remission of sins"). can be read that way. But if you look at the way the words are stacked, it does not require that interpretation.
Sometimes you are doing something (for) to get something, and sometimes you are doing something (for) because of something else. For example, I am receiving this award for an accomplishment I have completed. We should be baptized in virtue of the forgiveness of our sins.
To get a definitive word regarding this issue, I go to Acts 10. As Peter is giving the Gospel, the people believe, and there is a manifestation of the Spirit. Peter realized they had been given the Holy Spirit just “as we have been.” By Peter’s assessment, they are brothers and sisters in Christ. If baptism were necessary for regeneration, these Gentiles would not have been regenerated before they were baptized.
Clearly, baptism is important, commanded, and critical for a whole lot of reasons. But one of those reasons is not to get regenerated.