When you have attended church for a long time, especially in a culture where Christianity enjoys a lot of influence, a familiar language is developed, in this case Christianese where it is commonly assumed everyone understands what is being said. The problem is with some of these terms, even those that come out of the Bible, have such a storied history in the church and culture the original meaning is sometimes literally lost in translation. One of such words is baptism. Like apostle, angel, evangelist, deacon, Christ, they are all words that have not been translated but rather transliterated, that is, English Bible translators tried to reproduce the sound of the word in the original language in English. Many of these translation decisions were made centuries ago and out of respect for the tradition they have been preserved. The trouble is the further we move away from the Bible times and culture, the meaning of these words become obscured through our own theological and cultural lenses. As I explained in The History of an Idea, we have to go into the past to determine how a word developed its meaning in the present.
Baptism, baptisma in the Greek, is from the Greek verb baptizo which means to dip or immerse. In Greek it was used in a variety of ways such as immersing something in water, washing something or dying fabric. In other words, baptizo was pretty ordinary word and did not inherently have any of theological or ecclesial overtones it has today. John being called the Baptist does not mean he was a member of the Southern Baptist Convention or refer to what happens in a Roman Catholic setting where a priest pours water over an infant initiating them into the church. Some modern translators prefer to call him John the Immerser to avoid all the baggage associated with the word. Now to sidestep the accrued meanings we have to go back to the original context of 1st century Roman Palestine to understand how the word is used in the New Testament.
The particular form of baptizo, baptisma, occurs only within the New Testament and not anywhere else in Greek literature and it has a cultic sense to it along with other more common form, baptismos which has the same meaning. Cultic here is a technical word meaning it has a religious connotation. Now the Greeks had sacral pools and so did the Jews so baptism, as it is used in the NT meant a ritual washing. The aim was not to make something not dirty or remove germs (which they had no concept of anyway) but to make something ritually pure. For example in Hebrews it says,
Therefore let us leave the elementary doctrine of Christ and go on to maturity, not laying again a foundation of repentance from dead works and of faith toward God, and of instruction about washings (baptismos), the laying on of hands, the resurrection of the dead, and eternal judgment. – Hebrew 6:1-2 ESV
Here, instead of going with the older convention that appears in the King James Version for example, they properly translate it as washing, as in ritual washing. Now there were different types of ritual washing in that world. The most significant type for the New Testament is the one the prophet John performs which lends him the famous moniker “The Baptist.” It is significant it is the first instance of ritual cleansing we are introduced to in the New Testament narrative which is then appropriated by Jesus, performed by his disciples and takes on a significant symbolic meaning in the early Church.
Dr Craig Keener in his bestselling New Testament Background Commentary writes,
Of the many kinds of ceremonial washings in Jesus’ day, the most significant once-for-all kind of washing was proselyte baptism. Gentiles were usually baptized when they converted to Judaism; this was widely known and is even mentioned by the Greek philosopher Epictetus. By reporting that John asks Jews to be baptized in an act of conversion, the Gospel writers suggest that John treats Jews as if they are pagans, which was unheard-of…
A proselyte is a Gentile convert to Judaism. Therefore, baptism was a one-time conversion rite initiating a person into the community of God’s people. In Jewish thinking, by their ethnic heritage they were the holy people of God and the Gentiles were therefore unclean simply due to not sharing their Jewish heritage. Therefore to become a Jew, which was more than a change in one’s religious belief but also a change in one’s identity including nationality and ethnicity, they had to be washed of their Gentile uncleanliness. John was preaching an eschatological (end time) message that God was returning to his people, bringing to an end the former world and ushering in a new age, therefore they had to ready themselves. They automatically thought being Jewish by descent was enough to qualify for the status of being a member of God’s covenant people as well as keeping the law. John however said it was not enough (Matthew 3:9.) They could not rely on their heritage because God required true obedience from the heart so they needed as radically a change as a Gentile becoming a Jew (Matthew 3:7-10.). In the particular context of John, baptism was an initiation rite into an eschatological community: the faithful, end time people of God who will be saved.
Jesus adopted baptism since John was his forerunner and he too carried on that eschatological vision of a renewed, covenantally faithful, people of God, which was fulfilled in and through his person. John immersing people at the Jordan, the same river they had to cross when they were first entering the Promised Land, meant they were becoming the covenant people, on the covenant land, obeying the covenant God anew. A true transformation. After Jesus was immersed by John, God said to him, “This is my beloved son, with whom I am well pleased.” This was a not a heavenly declaration of Jesus’ divine status. Though Jesus is clearly divine in the New Testament the title “Son of God”, as I have pointed out many times before, is not a divine title. The New Testament took the term from the Old where it primarily meant an Israelite, particularly a faithful member of God’s covenant people. Jesus is portrayed in the gospels and elsewhere in the NT as well as the new, faithful Israel (Matthew 2:15; Galatians 3:16; Revelation 21:12-14.) So the heavenly voice was a public declaration that Jesus was the embodiment of faithful Israel. John’s baptismal ministry was to point to Jesus as the true Israel so they follow him and be incorporated into him, the true Israel. This carried forward to the early church through Jesus’ command where baptism was a conversion rite initiating them into the Church, the new Israel, the people of God in Jesus the Messiah (Ephesians 2:11-13.)
So just like with Gentile proselytes you gained a new identity in the Messiah, becoming a new creature altogether (2 Corinthians 5:17.) This change with proselytes was described as being “born anew” and that is how Jesus described what it meant to follow him (John 3:3.) While water baptism was a ritual sign of this dramatic change, John pointed to Jesus who would “baptise in the Spirit.” Though it was his followers, never Jesus, who administered the water ritual, he was the one who caused the dramatic, fundamental spiritual change. Jesus would immerse people, cleansing them with God’s own holy spirit. This has various resonances in the Old Testament particularly with passages like Ezekiel 36:25-27, which is found in the context of the redemptive renewal of the people of God and the fulfilment of the ancient covenant promises. In New Testament theology, those Jewish promises are fulfilled in the Messiah Jesus (2 Corinthians 1:20.)
Baptism, like many other things in the New Testament, has a thoroughly Jewish meaning. Remember Christianity began as a sect within second Temple Judaism. When we forget it’s quintessentially Jewish roots we lose sight of what it all means. However baptism, as a symbol of radical transformation, acquired a new meaning in the early church even though it still had earlier Jewish precedents. From an excerpt in an earlier post based on the work of NT Wright I write,
Even though resurrection was a belief in a literal event it was used metaphorically without eschewing its concrete referent. In post-exilic writing it was a metaphor for the restoration of Israel. Early Christian resurrection beliefs modify this, moving away from a nationalistic, ethnic focus to a new set of metaphors such as baptism and new birth. Again these new metaphors have a literal concrete referent in bodily resurrection. However, there is a radical change in resurrection symbolism from second Temple Judaism to early Christianity. New and different metaphorical meanings emerge in the early Jesus movement, shedding the old usages.
Simply put, baptism became a metaphor for the resurrection of Jesus. So to be baptised symbolically and metaphorically meant participating in the death and resurrection of Jesus thereby being incorporated into him and the community of his followers.
In summary ritual washing of various forms was common in the ancient world of the New Testament. John came up with a prophetic, ritual innovation in immersion that had an eschatological focus, which was necessarily adapted by Jesus and his followers, and after his resurrection acquired a new symbolic meaning in the early church. We can be certain that in the New Testament the conversionary rite happened by being dipped into a body of water and was a fully cognizant choice so only those mature enough to make the choice participated in it. This however does not mean the New Testament necessarily affirms everything about modern credobaptism, that is the practice of only baptising confessing adults. Baptism, that is, being dipped into water was a mandatory initiation rite into the community of believers and not a particular denomination. It was a symbol of unity and not our current fragmentation. This physical act became a metaphor for participation in the Messiah as well as spiritual regeneration by virtue of having a new identity in our resurrected Lord.
But when the goodness and loving kindness of God our Saviour appeared, he saved us, not because of works done by us in righteousness, but according to his own mercy, by the washing of regeneration and renewal of the Holy Spirit, whom he poured out on us richly through Jesus Christ our Saviour, so that being justified by his grace we might become heirs according to the hope of eternal life. – Titus 3:4-7 ESV
 βάπτισμα, Kittel, Gerhard; Friedrich, Gerhard; Bromiley, Geoffrey, Theological Dictionary of the New Testament (Abridged), p.93.
 Craig Keener, The IVP Bible Background Commentary: New Testament 2nd Edition, p. 251, IVP, 2014.
 Ibid., p. 255.