NOTES for Деян 2:14-21
Addressing the crowd, Peter first defends the apostles against the accusation of drunkenness; this was vitally necessary to establish the seriousness of the apostolic proclamation. Unfortunately, in our time Peter’s argument that people could not be drunk because it was not the hour for drinking would not work: customs have changed greatly, and lovers of alcohol get drunk at any time... But whatever opponents may say, both those of that time and those of later times, Christianity is inseparable from sobriety understood more broadly than abstinence from alcohol: faith gives the most sober possible view of reality.
In noting the similarity between what was happening and what the prophecy of Joel had foretold, Peter relies on an Old Testament prophecy not because he wished to drag in a justification from ancient books by force. Yes, he is addressing people who need an argument based on the books of the Old Testament, but the point is that Peter truly sees the Old Testament prophecies actually unfolding before the eyes of those gathered.
The more we compare the Old and New Testaments, the more we will be able to see their interconnection.