Is baptism essential for salvation?
The short answer to your question is "absolutely not". Salvation comes "by grace through faith" (Eph.2:8-9). And whatever is of faith is by definition not of "works", that is, not as a result of something we have done (Rom.3:28; cf. Gal.2:16; Eph.2:9). God calls upon sinful, unsaved mankind to repent of dead works of the flesh (Heb.6:1; cf. Matt.4:17) and turn to Him by putting our faith in the person of the Son of God and in His work on the cross for us, dying for us and thereby cleansing us from our sins. So to add water baptism or any other condition to salvation by definition makes the process one of works rather than of grace. In fact, anyone relying as a guarantee of salvation on the fact that they were baptized with water is badly mistaken. Salvation is by faith in Jesus Christ, pure and simple, not by any ritual or organizational membership. Whenever anyone attempts to add to God's requirements for salvation they are putting those who listen to them at risk, because anyone who thinks they are saved because they have been baptized is wrong according to scripture, and if such a person is not a believer in Christ, then it is not only a matter of having a warped view of salvation but of not having salvation in the first place.
But whatever I had gained [in my former godless life], compared to Christ I have come to consider these things as losses. Indeed, I consider everything to be a loss compared to the surpassing importance of knowing Jesus Christ my Lord, for whose sake I have suffered the loss of everything, and consider [everything I have lost] as garbage, compared to gaining Christ, and being found in Him - not having a personal righteousness [developed] through [following] the [Mosaic] law (i.e., works) - but having that righteousness [that comes] through faith in Christ, that righteousness [that comes] from God based on faith.
Water baptism is also known as John's baptism. This was a ritual closely associated with the return of the Messiah and the preparation of the Jewish nation for that return, preparing the hearts of the willing for Jesus' arrival through an act that acknowledged repentance from sin. Jesus would change the ritual into a reality when He, having accomplished eternal redemption of sin at the cross, ascended on high and made possible the predicted "baptism of the Spirit" (Matt.4:11), the true baptism of the Church whereby everyone who believes in Jesus since the day of Pentecost is both anointed with the Spirit and made one with Jesus through the Spirit. This is the "one and only" baptism of which the scriptures speak which comes as a result of the "one and only" faith, the faith we have and maintain in Jesus Christ (Eph.4:5).
It is true that there is much water baptism in the book of Acts - but this was a transitional period wherein even the apostles were in the process of learning what the new realities of the cross, Jesus' resurrection, ascension, and session, and the coming of the Spirit at Pentecost truly meant (as Peter's experiences in Acts chapter 10 show so clearly). It is true that most Christian traditions engage in some form of water baptism, but given how wrong most denominations are about so many things this is a hardly an argument. We have to look to what scripture has to say, and whenever and wherever we do, we find that the Spirit's baptism is what is really important, as John the baptist predicted even before the fact:
John answered them all and said, "I am [symbolically] baptizing you with water. But One who is more powerful than me is coming, [One] whose sandal thong I am not sufficient to untie. He will baptize you with the Holy Spirit ..... and with fire! His winnowing fork is in His hand, [ready] to cleanse His threshing floor and gather the grain into His barn, but He will burn up the chaff with unquenchable fire.
One major problem with water baptism is that if you ask the people and groups who do it what it means you are likely to get a variety of widely divergent answers. This can only show that there is a problem with the symbolism behind present day water baptism as it is currently practiced. At best it may represent our new relationship with Jesus and our faith in Him, but this is usually very confusingly explained in ceremonial baptisms. The real impression that water baptism leaves upon people is that this is some sort of essential ritual without which you can't get to heaven - exactly the thing you are asking about. And while there is nothing in the Bible to even suggest that, many groups brazenly proclaim just that. "Water-baptism as essential to salvation" is a very dangerous heresy, because as explained above it can lead people to relying upon a human ritual instead of God's spiritual realities. But it also has the added danger of making people who buy into this deceit entirely dependent upon the people doing the baptism. After all, if baptism were essential to salvation, then you better "have it done right". If it's essential for salvation, then it must be imparting some special grace. And if all this is so, then it would stand to reason that only those who have the special "in" with God necessary to water-baptize correctly can save you. So a person who buys into this deceit of necessity becomes enslaved to the group or persons who are making these claims. If someone else other than God is in control of your salvation, then they become a "god" to you (and this is typical modus operandi in all cults). In my experience and observation, water-baptism, while potentially harmless because it is unnecessary, has caused more false guilt and more mistaken reliance upon human beings, ritual, and far from godly organizations than perhaps any other fallacy. We do want to do what God wants us to do, but apart from Jesus' command to His disciples that they should be baptizing (note, not "be baptized" but "baptize others"), there is nothing in scripture that commands us to partake of this ritual. And when we look at it carefully, we find that Matthew 27:18-20 is actually also talking about the baptism of the Spirit. For water baptism could never (as the Greek text literally says) baptize us "into the persons" of the Father, Son, and Holy Spirit - but Spirit baptism does precisely this, making us one with Christ as Christ is one with the Father and the Spirit.
So now, there [awaits] no judgment of condemnation for those who are in Christ Jesus. For the law of the Spirit of life in Christ Jesus has freed you from the Law of sin and death.
Clearly then, we are "in Christ" and have the eternal life that frees us from the "law of sin and death" through the Spirit's baptism, not through any water ritual. No human being can "put us into Christ", making us one with Him. Only God can do that, and does just that through the baptism of the Spirit whenever anyone puts their faith in Jesus Christ. Water baptism these days almost always takes place long after a person has believed in the Lord, and long after those who gave the gopsel have carried out our Lord's command to be "baptizing them into" His person. By sharing the gospel, people believe in Christ unto salvation and are then baptized into Him, becoming one with Him and the Father and the Spirit through the Spirit's ministry of baptism. No amount of water administered through human hands could ever hope to accomplish anything of the sort.
In conclusion, water baptism, while potential harmless and even possibly of some small benefit if it is used to teach by analogy how we become one with Christ, submerged into Him as the water image suggests, in practical terms has been used historically as a casus belli between denominations, a tool for manipulation of adherents in all sorts of groups, and, most sadly of all, a substitute for a true saving faith in Jesus Christ in far too many cases.
I hope that this answer will prove of some help to you. Please see also the following links:
Baptism: Water and Spirit.
Baptism: Water and Spirit II.
John's Water-Baptism versus the Baptism of the Holy Spirit
One Baptism: the True Meaning of Peter's Words at Acts 2:38.
Is water baptism required of Christians today?
Baptism and salvation.
Does baptism play a role in being born again?
Feel free to write me back about this.
In Him who underwent the baptism of the cross (Lk.12:50; cf. Mk.10:39) that we might be baptized with His Holy Spirit and have life forever with Him through faith in Him and what He has done for us, our dear Lord and Savior Jesus Christ.