into, unto, to, towards, for, among
“For” (as used in Acts 2:38 “for the forgiveness…”) could have two meanings. If you saw a poster saying “Jesse James wanted for robbery”, “for” could mean Jesse is wanted so he can commit a robbery, or is wanted because he has committed a robbery. The later sense is the correct one. So too in this passage, the word “for” signifies an action in the past. Otherwise, it would violate the entire tenor of the NT teaching on salvation by grace and not by works.
John came baptizing in the wilderness and preaching a baptism of repentance for the remission of sins. (Mark 1:4, NKJV)
And he went into all the region around the Jordan, preaching a baptism of repentance for the remission of sins, (Luke 3:3, NKJV)
“after John had first preached, before His coming, the baptism of repentance to all the people of Israel. (Acts 13:24, NKJV)
Then Paul said, “John indeed baptized with a baptism of repentance, saying to the people that they should believe on Him who would come after him, that is, on Christ Jesus.” (Acts 19:4, NKJV)