I had to chop out from Scriptural quotations cuz this post was too long, but I left the verse numbers in so you can look them up : )
1 Peter 3:18-22
Up to this point in the chapter, Peter is essentially giving some nice thoughts, and then introduces this clause by the conjunction ‘oti (because). The context of the clause is established at its beginning: “Because Christ also died once for our sins…” Then we fastforward a bit: “Whereunto baptism being of the like form, now saveth you also…” The “saveth” is taken to be in regard to “sins” due to the context of “Christ died for our sins”, and also it follows with: “not the putting away of the filth of the flesh, but the examination of a good conscience towards God by the resurrection of Jesus Christ.” We have a good conscience when we are cleansed from sin; Peter specifically negates the idea of some kind of physical “saving”, or “cleansing”.
The “saving” which appears in conjunction with Noah’s Ark is “diasozo”; the preposition “dia” turning the meaning of the word into something akin to: to bring safely through. The “saving” of which Peter speaks of baptism doing is merely “sozo”, to save. Among other places “sozo” appears in reference to Christ’s salvation of us is Acts 4:12, Mark 16:16 (coincidentally another verse teaching baptismal regeneration), 1 Cor 15:2, Matt 10:22, Mark 13:13, among many others.
Similarly, if Peter had meant to say that baptism was an act of obedience to God which proclaims that we are a Christian, would it not be odd for him to use the word “sozei”, an inflection of the word “to save”? Would he not rather say something to the effect of, “baptism, which is now the proclamation of your faith in Christ”?
The construction of this verse in Greek is something like: “if not who begotten of water and the spirit not he is able to enter into the kingdom of God”. Not he is able. Why “not he is able”? Because original sin is still upon him, and “nothing unclean shall enter it [Heaven]”. The concept of the Spirit coming through baptism is testified in Matthew 3:16-17.
Baptism is connected with the remission of sins, and the reception of the Holy Ghost. This is made abundantly clearer in Acts 22:16, where repentance is not even brought into the discussion as a possible confusion.
In Galatians 3:27, Paul teaches that we clothe ourselves with Christ upon baptism; he does not say we do upon belief. In Titus 3:5, he makes a definitive statement: “Not by the works of justice, which we have done, but according to his mercy, he saved us, by the laver of regeneration, and renovation of the Holy Ghost;”
Coincidentally, “he saved” is from an inflection of (you guessed it!): sozo. What did early Christians believe about baptism?
“Regarding [baptism], we have the evidence of Scripture that Israel would refuse to accept the washing which confers the remission of sins and would set up a substitution of their own instead [Ps. 1:3–6]. Observe there how he describes both the water and the cross in the same figure. His meaning is, ‘Blessed are those who go down into the water with their hopes set on the cross.’ Here he is saying that after we have stepped down into the water, burdened with sin and defilement, we come up out of it bearing fruit, with reverence in our hearts and the hope of Jesus in our souls” (Letter of Barnabas 11:1–10 [A.D. 74]).
Hermas wrote: “‘I have heard, sir,’ said I, ‘from some teacher, that there is no other repentance except that which took place when we went down into the water and obtained the remission of our former sins.’ He said to me, ‘You have heard rightly, for so it is’” (The Shepherd 4:3:1–2 [A.D. 80]).
Theophilus of Antioch: “Moreover, those things which were created from the waters were blessed by God, so that this might also be a sign that men would at a future time receive repentance and remission of sins through water and the bath of regeneration—all who proceed to the truth and are born again and receive a blessing from God” (*To Autolycus *12:16 [A.D. 181]).
Clement of Alexandria:“When we are baptized, we are enlightened. Being enlightened, we are adopted as sons. Adopted as sons, we are made perfect. Made perfect, we become immortal . . . ‘and sons of the Most High’ [Ps. 82:6]. This work is variously called grace, illumination, perfection, and washing. It is a washing by which we are cleansed of sins, a gift of grace by which the punishments due our sins are remitted, an illumination by which we behold that holy light of salvation” (*The Instructor of Children *1:6:26:1 [A.D. 191]).
To name a few.