Is water baptism absolutely necessary before a person can be saved?
Let's you and I suppose that a person, under the conviction of the Holy Spirit, believes in Jesus as their Savior (Rom. 10:9;), they repent of their sins and receive Jesus Christ as their Saviour (John 1:12). Is that person saved? Of course they are. Let's further suppose that this person confesses his or her sinfulness, cries out in repentance to the Lord, receives Jesus as Savior and then as they are walking across the street to get baptized at a local church they get hit by a car and are killed. Does that person go to Heaven or hell? If they go to Heaven, then baptism is not necessary for salvation. If they go to hell, then trusting in Jesus by faith is not enough for salvation which, in its totality, is contradictory to everything the Bible teaches. Again, saying that baptism is necessary for salvation is dangerous because it is saying that there is something that "we" must do to complete salvation. That is wrong!
Now, if we are saved by faith (which is the core teaching of Scripture) then we are saved by faith the very moment we repent and ask Christ into our heart, not when we get baptized. If baptism is necessary for salvation then this means that we are not justified by faith which would contradict the whole of Scripture. Also, if baptism is necessary for salvation, then all babies who die go to hell since they weren't baptized. If baptism is necessary for salvation, then Jesus lied to the thief on the cross to whom He promised, “Today you will be with Me in Paradise.” The thief was not baptized and yet Christ assured him that his salvation was both assured and secured because of his faith and nothing else.
The reason baptism is not necessary for salvation is that we are justified by faith alone (Rom. 5:1; Eph. 2:8) and not by a "ceremony." Of Abraham (for example) the Bible states simply that “Abraham believed in God, and it was counted unto Him for righteousness." We are saved by faith alone, faith in the atoning blood of Jesus Christ, and nothing else. The Bible always places the foundation of Salvation squarely on “faith” and never on anything else. To depend on baptism as being “necessary” is to proclaim that Jesus’ Sacrifice of Himself upon the Cross was somehow ineffective. Now, those who erringly believe that baptism is necessary for salvation will turn to verses such as 1 Pet. 3:21. However, that Scripture speaks only of ‘the baptism into Christ’ which takes place at conversion by faith. Or, Acts 2:38 which is often erringly used to say that baptism is part of salvation, but we know not only from other scriptures but from Jesus Himself that it is not. Those scriptures have nothing whatever to do with water baptism. It is through accepting Christ Jesus as Lord and Saviour and relying on Him Alone for justification and salvation that we become the sons of God. It is not the act of baptism that secures these things for us. The putting on of Christ (according to the Gospel) consists not in an outward work, but in a new inward birth.
However, all of that being said, though baptism is in no way "necessary" for salvation it is nevertheless a public sign and confession of our new birth in Christ. It is an outward representation of an inward reality. The reality of the inward washing of Christ's Blood upon the soul. So if your question, in part, is do I think that a person should be baptized then my answer is a simple “Yes.” Be baptized, but don’t rest the reality of your salvation in the act of baptism. Rather, make sure of the thing that it signifies, an established, completely new and everlasting life in Christ Jesus.