After Jesus ascends to heaven His disciples begin their ministry. Peter is the chief spokesman, as he is the Rock the church is built on (not in any weird Catholic way, just in a common sense “boy that sure seems like that’s what happened” way).
Peter preaches a scathing message against Israel for killing their Messiah. “What shall we do?” is the response of the audience, a great response which would melt any pastor’s heart.
Peter answers, “Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit.”
Note our two main themes here: forgiveness of sins and the Holy Spirit. Baptism circles around these themes all the time.
Many however stop here and say, “See? All they did was get baptized and they were saved. Just get dunked in water, that’s all you do.”
But as you should always do: keep reading! Get the whole context.
With many other words he warned them; and he pleaded with them, “Save yourselves from this corrupt generation.” Those who accepted his message were baptized, and about three thousand were added to their number that day.
Peter’s message was bigger than just, “get wet.” He warned them and pleaded with them. Also, those who were baptized first “accepted his message.”
“Accepted” is a pretty lame translation. The word is more accurately “gladly welcomed.” They received his words with joy and helped them move in!
This was no easy-believism, nor a flippant religious ritual they performed. This was a glad acceptance of a new way of thinking and living that follows sorrow over past errors, that’s what true repentance is.
Those who received Peter’s message were baptized. Faith is a thing. It’s not just getting wet. And remember, Peter’s message was not a happy message! It was a message of condemnation and warning. They received the rebuke and sought salvation and forgiveness for blowing it.
Baptism isn’t a formal ritual done once to take care of everything and then forgotten. It’s part of the whole salvation response.