My Bible does say that you must be born again (in spirit), baptism by immersion is a ritual which symbolizes the childbirth process - newborn baby emerges from the amniotic fluid in the womb, and the first thing to do is a loud cry to draw in air, that’s what the word spirit literally means - breath. In the beginning the spirit of God hovered above the water, you emerge from the water, you draw in spirit. If you do it by pouring or sprinkling, you lose this element, that’s more like raining on your parade which does nothing but gets you wet.
The word baptism, in its essence, means
washing. It is rooted in the Jewish practice of tevilah, ritual washing, especially the full immersion washing in a mikveh. Immersion was the normative mode of baptism in the early Church, and remains so in the Eastern Churches. But pouring has always been acceptable, because it was never about the amount of water and how much contact that water made with the body--it was about God's grace and the promise connected to that water (Ephesians 5:26), water
and word.
In John chapter 3 after Jesus talks about the need of new birth, and mentions water and the Spirit, Jesus then says to Nicodemus, "You are a teacher of Israel [aka a rabbi], how do you not know this?"
Why did Jesus expect Nicodemus to understand what Jesus was talking about?
Because baptism has its roots in Jewish water-washing practices.
When John the Baptist was out there in the Jordan baptizing for the purpose of repentance, to call Israel to repentance in the anticipation and expectation of the Messiah's coming, he wasn't doing something unrecognizeable in the context of Judaism. Ritual washing was normative in Judaism. The meaning of what John was doing was unique--a call of repentance and Messianic expectation.
Even today "baptism", though Jews don't call it that because it's a Greek word to translate a Jewish concept and has explicitly Christian overtones which Jews don't associate with, is still a regular practice in Judaism. Most noteworthy is the role tevilah in a mikveh plays in conversion to Judaism.
In Judaism a convert, one going from being a non-Jew to becoming a Jew, undergoes a ritual washing in a mikveh that signifies a person's new life as a Jew--their former life as a non-Jew is in a sense washed away and now they are now a Jew, a member of the Covenant People, a child of Abraham, a child of Israel. Jewish sources say this.
And, as an aside, when a family converts to Judaism infants are included in this conversion, they are also washed in the mikveh because the child is being converted to Judaism as well (this is in addition to, of course, circumcision for men/boys).
So when Jesus says to Nicodemus, "Why don't you understand this?" it's because Nicodemus, a rabbi, was not ignorant of what Jesus was saying. At least he shouldn't have been. So there is an open question of whether Nicodemus was genuinely confused or simply being stubborn.
So Christian Baptism, instituted by Jesus Christ, is the specific application of water in the form of a washing--a baptism--but with a new and distinctively Christian and Christocentric meaning. "Go make disciples of all nations, baptizing them" means that the Church is commanded to baptize for the purpose of welcoming people into the life of Christ and His Church, as disciples of Jesus who are to be trained and taught the things of Christ, "teaching them all which I have said".
The meaning of this Christian Baptism is then expressly taught throughout the writings of the New Testament:
St. Peter says, "Repent and be baptized, all of you, in the name of Jesus Christ, for the remission of your sins and you will receive the gift of the Holy Spirit" (Acts 2:38), that is a promise connected to Christian Baptism.
St. Paul says, "All of us who have been baptized into Christ have been baptized into His death" that by baptism we have been buried with Christ and raised with Christ. Romans 6:3-4
Paul, again, says that all who were baptized into Christ "have put on Christ" Galatians 3:27
Peter in his first epistle writes that the saving of Noah and his family through the flood by the ark prefigured baptism, baptism is the antitype--the fulfillment of the type of the water of the flood and the rescue through the flood--and thus "baptism which now saves you". How can water save us? It can't, but it's not cleaning dirt from the body Peter reminds us, but the cleansing of our conscience because we are made new in and with God by the resurrection of Jesus. That's what we receive in baptism, a clean conscience, a new conscience, a new self in relation to God that is empowered by the Risen Christ, His resurrected life is now the life which sustains us, and which we received in/with the waters of baptism.
Hyperfocusing on the mode of baptism is just legalism. It's not the quantity of water that matters. It's the grace and power of God, who by His word--right there connected with the water of baptism--makes us new people in Jesus Christ.
-CryptoLutheran