The risen Jesus pours out the promised Spirit, and Peter's sermon shows the last days have begun and calls for repentance.

Baptism into Christ Jesus is baptism into his death, burial, and resurrection. Paul's point is not that a ritual automatically changes a person, but that it marks a real union with Christ that changes who you are.

Peter's answer to a crowd cut to the heart names repentance, baptism, forgiveness, and the Spirit, and the church has read its grammar two ways ever since.