It is what the Apostle Paul teaches but it is also scripture.
2 Timothy 3:16-17
16 All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, 17 so that the servant of God may be thoroughly equipped for every good work.
Mark 16:16
16 Whoever believes and is baptized will be saved, but whoever does not believe will be condemned.
The main point being it is the one who doesn't believe is the one condemned. Not the believer who has yet to be baptised.
Secondly because if it truly took baptism to be saved from hell than there could be no death bed conversions and Jesus lied to the thief next to him on the cross. He said 'Today you will be with me in paradise" He promised the unbaptised thief heaven and I choose to believe that.
Scripture always interprets scripture, so all verses on being saved and baptism should be looked at, not one plucked out. It's an entire study.
Acts 2:38
38 Peter replied, “Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit.
The Bible is clear that salvation is by grace through faith in Jesus Christ, not by works of any kind, including baptism. We also know death bed salvation carried the promise of heaven, so a verse like this should bring further scrutiny as to the real meaning since it can't contradict the other clear teachings of scripture.
The word 'for' is used here and I believe it's this small word that has this verse being misunderstood. The Greek word used is eis and it can have several different meanings. Noted Greek scholars as A.T. Robertson and J.R. Mantey have maintained that the Greek word here is better translated as “because of” and not “in order to,”.
38 Peter replied, “Repent and be baptized, every one of you, in the name of Jesus Christ because of the forgiveness of your sins. And you will receive the gift of the Holy Spirit.
This verse is really about the fact that believers (those who have repented) should be baptised.
And repentance can not mean 100% sinless perfection after you are saved and or baptized and/or have repented only once as a one time act either, cause we all know Peter sinned that Paul pointed out, and Paul may have sinned when he caved into the Jews by having Timothy circumcised, etc, and while not as apparent, or recorded, I'm sure others still sinned sometimes after they were saved as well also, etc. Also the word "repent"or "repentance" can mean many different things as well, not the least/most of which has to do with, or has to mean, etc, 100% total and sinless perfection continually after you are saved, etc, or you might lose salvation, etc, it cannot mean that or nobody would be saved as evidenced from or by, even some of our own most highly esteemed apostles in our Bibles, so it cannot mean that...
I think it has to be an "attitude" or humble perspective or point of view or state of mind and heart continually after you have been saved, that you "walk in" when you sin or mess up, or realize you just messed up afterward, etc, and not that your always going to be, or are ever going to be, this side of life anyway, 100% totally and 100% sinlessly perfect and never mess up ever again after you are saved, etc, etc, etc.
I think it has to be an attitude or humble (and "repentant") state of mind and/or heart, etc, that you walk in after you are saved, or that is the true evidence or your being saved, and not complete 100% total 100% sinless perfection, etc. Otherwise I don't think anyone would be saved, etc, as evidenced by some of our very own most highly esteemed "people" who were saved and had already been converted in the Bible, and yet still messed up sometimes and/or still fell short sometimes, etc...
So, in conclusion, I think it is having the right kind of attitude when we do sin or mess up from time to time, etc, (the complete opposite of being proud, haughty, arrogant, etc), that we walk in after we are saved when we mess up, or realize afterward that we may have, or did mess up, etc, that is the most telling about our own state of salvation, etc...
But, I also don't think one can be saved and/or converted and be living a "hedonistic free for all lifestyle" either, or be purposely practicing one, etc, and truly be saved either, or not saved "yet", etc. If one is living that kind of lifestyle before conversion, then I would think they would have to "change" that or repent of that much, but no one is not ever going to never ever mess up in no kind of way ever afterwards either, that's just not possible for us, etc, and I think it is our attitudes when we do mess up or realize we have messed up, or did or may have messed up, etc, that are the "most telling" about our own state of salvation, etc...
God Bless!