Let’s start off with this passage:
1 Peter 3:21
There is also an antitype which now saves us—baptism (not the removal of the filth of the flesh, but the answer of a good conscience toward God), through the resurrection of Jesus Christ,
I think this pretty clearly defines the baptism that saves us as the answer of good conscience toward God, and even underscores it not to be a washing. That’s the solution to successfully passing Mark 16:16 test:
Young’s Literal Translation (YLT)
16 he who hath believed, and hath been baptized, shall be saved; and he who hath not believed, shall be condemned.
To properly understand the baptism passages, we need to understand that there are different kinds of baptisms in the Bible:
6 Therefore, leaving the discussion of the elementary principles of Christ, let us go on to perfection, not laying again the foundation of 2 of the doctrine of baptisms, … .
Even as far as water baptism is concerned, there are several kinds mentioned in the Bible. For the purposes of this post, I will look at the (non-water kind) baptism into Christ, and the water baptism which represents that.
That passage was from Peter. Let’s now hear from Paul. Consider this passage:
1 Corinthians 1:14-17
14 I thank God that I did not baptize any of you except Crispus and Gaius, 15 so no one can say that you were baptized in my name. 16 (Yes, I also baptized the household of Stephanas; beyond that, I don’t remember if I baptized anyone else.) 17 For Christ did not send me to baptize, but to preach the gospel — not with wisdom and eloquence, lest the cross of Christ be emptied of its power.
From the context, we can see that it’s talking about water baptism specifically. In v.17 specifically Paul defines the parameters of his apostolic mission. I believe if water baptism was a requirement to be fulfilled prior to being able to receive salvation, Paul would have phrased this passage and especially v. 17 very differently. So, if Paul wasn’t sent to water-baptize but to preach the gospel, and if without baptism you can’t be saved, who is doing the baptism? The Holy Spirit of God does, the moment you place your trust on Jesus for salvation – here’s another nugget from Paul:
1 Corinthians 12:13
13 For by one Spirit we were all baptized into one body—whether Jews or Greeks, whether slaves or free—and have all been made to drink into one Spirit.
The agent of this baptism is the Holy Spirit (not a human being), and the medium is the body of Christ (not water). This is supported by what Paul said elsewhere:
25 And he is not served by human hands, as if he needed anything. Rather, he himself gives everyone life and breath and everything else.
Water baptism in the Christian context simply symbolizes a specific one-time literal baptism (i.e., immersion) into Christ in the realm of the spirit (whereby I become a member of his body – i.e., a one-time immersion into Christ). The old dies, the new gets born again and is placed into Christ.