Acts 2:38 wasn’t Peter’s idea, and it obviously wasn’t mine either. I heard this conversion teaching from the Lord’s words to his apostles, in the gospels, and then to us in Acts. That was over 32 yrs ago. I heard and obeyed his rebirth instructions (not without first being offended at someone questioning my belief in Jesus Christ).
If you had never heard it taught before reading it here on this forum, then now you have.
Who else has heard it in the past, and chose not to regard those instructions from the Lord? Who hasn’t heard yet? Those are questions that we don’t know the answer to.
**So, tell me, if someone believes, puts their trust in Christ for salvation, and dies without being baptized, where do they go? Heaven or hell?**
If I knew for certain, I would be God. Mark 16:16 is some ‘tough love’, showing that he is being very firm in his ‘red line in the sand’. It is to be compared along with the Lord’s other words of commission in Matt. 28:19; Luke 24:47; and John 20:23. Again, those are His words, not mine.
IOW, no answer.
Then you are in no position to teach as truth something that you say God isn’t clear on.