Can anyone show me a Bible verse that says we get baptized to demonstrate something?

Acts 2:38 (baptism AFTER repentance), 1 Peter 3:21

EDITED TO ADD: I did look up that verse, and I think the instructions were "make disciples, baptize, and teach". I definitely think people continue to be taught after being baptized (most of Paul's letter were to baptized Christians teaching them various things), but I think the instructions to be baptized were given to "disciples", i.e., people who had decided to follow Christ. God bless!

Consider the baptisms before Jesus began His ministry. John the Baptist/Baptizer preached a baptism of repentance. As I understand it, those who came to John's "campaign", for lack of a better term, heard the message, repented, and submitted to baptism in the river Jordan. This apparently had nothing to do with salvation--John didn't tell people to become believers, but always to prepare the way of the Lord, bring forth fruits keeping with repentance, etc. Luke chapter 3 tells the story better than I can.

Three thousand Jews alone were baptized after they heard the message on the Day of Pentecost. Their salvation is not in question here, as Peter said, "Repent and be baptized"--he never exhorted them to accept Jesus as Savior, and so forth. We don't know if they were believers or not, and that's not the point: the one thing for sure is that 3000 Jews heard, believed, and were baptized. Would they have been baptized if they didn't believe Peter's message?

Still another example is in Acts 19. There were 12 followers of John the Baptist--in Ephesus, of all places!--and when the Holy Spirit came upon them, they were baptized.

As I understand Dr. Luther's philosophy, he wanted to baptize infants so that their souls would be saved and wouldn't be snatched away by Satan--forgive me, please, if I misquoted or mis-applied Dr. Luther's words, etc. He was, after all, trained as a monk and priest and didn't plan to start a new church or movement--he didn't have much of a choice, though, after he was excommunicated! I don't believe he did or practiced anything wrong but let it never be forgotten that he believed salvation came by hearing, and hearing by the Word of God.

I will try, because I personally believe that baptism is for someone who believes- it is not a magic rite that "christianizes" a person!

Washing of regeneration: Eph 5:26 That he might sanctify and cleanse it with the washing of water by the word,

Tts 3:5 Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost;

It seems one can be baptized as a baby, yet grow up totally an unbeliever- we all have seen this! Baptism is not the actual "thing" that saves one!

Mar 16:16 He that believeth and is baptized shall be saved; but he that believeth not shall be damned.

Acts is full of people who believe first, then ask to be baptized: Act 2:41 Then they that gladly received his word were baptized: and the same day there were added [unto them] about three thousand souls.

Act 10:47 Can any man forbid water, that these should not be baptized, which have received the Holy Ghost as well as we?

Baptism is a sign of the washing of repentance unto belief! ANd a symbol of "dying to sin"

Rom 6:3 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death?

1Cr 12:13 For by one Spirit are we all baptized into one body, whether [we be] Jews or Gentiles, whether [we be] bond or free; and have been all made to drink into one Spirit.

Colossians 2:12

buried with Him in baptism, in which you also were raised with Him through faith in the working of God, who raised Him from the dead.

Baptism symbolizes the death, burial (submersion) and resurrection (raising up out of the water) of Jesus Christ.

Check out the baptism of Jesus. It is to die to the flesh and be born in the spirit.

http://www.fbbc.com/messages/baby_dedication.htm Also there is a lot of grown people getting baptized in the book of Acts