NOTES for Act 2:37-38
As we can see, the people who heard Peter took his preaching seriously. The question "So what should we do?" did not sound by chance. In fact, if this concerns the rejection of the Messiah Himself, and a conscious one, there is no escaping the consequences of such a sin. Both Yahwism and Judaism traditionally viewed conscious sin as something whose consequences weigh over a person endlessly, even if that person deeply and sincerely repents of what he has done. And here the sin was participation in the death of the Messiah... There was something to think about and something to fear.
Peter immediately points the people listening to him to the only possible way out of the situation. It is a way out made possible precisely thanks to the One whom, according to the apostle's word, people killed and God raised. And this way out is connected with the possibility of sharing in that new life, the life of the Kingdom, which on the day of Pentecost became a reality open to everyone.
Entering the Kingdom, a person begins his life anew. From a clean slate. The consequences of all the sins he has committed remain in the former life, provided, of course, that the person does not drag them along with him. And so that this does not happen, the very conversion of which the evangelist speaks is necessary. In the Synodal translation it is traditionally called repentance, but the matter is precisely conversion: the corresponding Greek word of the original, at least, means exactly this. And conversion is not only a return to the God from whom one has turned away. And not only emotional remorse over sins committed.
It is also reflection on what one has done, awareness of the spiritual quality of one's actions, of the intentions that stand behind them. And it is a conscious rejection of those among them that are incompatible with the Torah, with the Gospel, and with the commandments given by God. Then one can truly begin a new life from a clean slate. Then the communal life described by the author of Acts could also become a reality: after all, it can exist only as long as every member of this community lives the life of the Kingdom in all the fullness available to him. As it should be in the Church with a capital C.