The surprising thing about that first reading is that after Peter and the others talked to the Pentecost crowd in Jerusalem they went on to baptizing three thousand people. That leads to all kinds of questions.
Like, where did they do it?
What words did Peter and the others use?
How could they have done it so quickly when later on the Apostles set up a three year training program for converts?
I don’t know the answers to those questions. It seems to be at odds with everything we know. It could take us older people back to 1941 when the U. S. Army began a three-month training program for new officers, and the cadets who had labored through four years at West Point complained bitterly about the ninety-day-wonders.
To go on with unanswerable questions, what happened afterwards to those three thousand people baptized that day? Well, I guess we see a good answer to that in the later chapters of The Acts of the Apostles where we see them setting up commune-like communities in which people lay all hey owned at the feet of the Apostles.
If you ask if in becoming Christians they gave up being Jewish, the answe would be, “No.” Their Jewishness didn’t seem to be a contradiction to them. The only thing that became different was that they bent kosher rules by eating along side Gentile Christians who enjoyed bacon.
Almost fifty years would pass before the Pharisees would begin insisting that Jewish Christians could not have it both ways. The Pharisees told them they would have to stop eating with Gentiles if they wanted to be recognized as Jews. Matthew wrote his Gospel as a denial of that stand the Pharisees were making.