According to Leviticus 23:17, Jews were required to come to the temple on Pentecost from wherever they lived. So devout Jews living in many nations were present for the events Luke records here. Since they were from different nations, they spoke different languages. In chapter 1, Luke let his readers know of the importance of the coming of the Holy Spirit in enabling Jesus’ followers to reach others with the message of Jesus. This can be seen very clearly here. One of the ways is that Peter, who has previously been afraid to risk his reputation by defending Jesus, is now preaching openly about him. Another is that the people listening to Jesus’ followers were all able to hear the message in their own language. These followers were all from Israel and didn’t speak those languages, yet they were able to speak in languages they had never learned. As a result of Peter’s and the other Apostles’ preaching, 3000 trusted Jesus that day. This was the birth of the church. They immediately began to meet together both in large gatherings in the temple courts and in people’s homes.
Even today, when people trust Jesus, they receive the Holy Spirit. Not so we can feel superior or have special powers that impress others, but to enable us to reach others with the message of Jesus. It’s a privilege we should not take for granted nor an obligation we should ignore.