And they were all filled with the Holy Spirit and began to speak in other tongues as the Spirit gave them utterance.  Now there were dwelling in Jerusalem Jews, devout men from every nation under heaven.  And at this sound the multitude came together, and they were bewildered because each one was hearing them speak in his own language.  And they were amazed and astonished, saying, “Are not all these who are speaking Galileans?  And how is it that we hear, each of us in his own native language?  Parthians and Medes and Elamites and residents of Mesopotamia, Judea and Cappadocia, Pontus and Asia, Phrygia and Pamphylia, Egypt and the parts of Libya belonging to Cyrene, and visitors from Rome, both Jews and proselytes, Cretans and Arabians—we hear them telling in our own tongues the mighty works of God.”  Acts 2:4-11

After Jesus’ ascension, His disciples return to Jerusalem to wait for the Holy Spirit to come and empower them to do the work of ministry.  While they are held up in a house in Jerusalem, on the day of Pentecost, the Spirit of God comes and enters the house where they were staying and enters into each of them.  Shortly after, Luke says they were all filled with the Holy Spirit and began to speak in foreign tongues. 

In Acts 2:5, we are also told that there was staying in Jerusalem devout Jews from every nation under heaven.  There were many Jews who at this time in the first century were living all over the known world who were in town because of Pentecost.  This Jewish holiday, also known as the Feast of Harvest, was an important one.  It was one of the three feasts God told His people to keep every year in Exodus 23.  He told them, Three times in the year you shall keep a feast to me….you shall keep the Feast of Harvest, of the firstfruits of your labor.

So the Feast of Harvest (Pentecost) was very important, which is why there were Jews in town from all over.  In verse 6 we are told they hear this sound—probably the sound of the loud and violent wind.  So they follow the sound and gather at the house where Jesus’ disciples were staying and they witness this group speaking in foreign languages.  Luke says in Acts 2:6,

And at this sound the multitude came together, and they were bewildered, because each one was hearing them speak in his own language.

The word for language used here is the Greek word dialekto.  It's here we get our English word dialect.  It refers to an earthly language.  So they heard this group of Jews speaking in their own dialect—in their own language and they were amazed. 

They say in Acts 2:7, Are not all these who are speaking Galileans?  They knew these uneducated Galileans would not know how to speak all these different languages.  Notice how many were being spoken.  Luke says in vv. 9-11,

 Parthians and Medes and Elamites and residents of Mesopotamia, Judea and Cappadocia, Pontus and Asia, Phrygia and Pamphylia, Egypt and the parts of Libya belonging to Cyrene, and visitors from Rome, both Jews and proselytes, Cretans and Arabians.

Why does Luke take time to list all these out?  I believe one reason is that he wanted to highlight the miraculous nature of this event.  The disciples were not just speaking in one or two foreign languages.  Notice Luke mentions 15 or more people groups represented here.  There are all kinds of languages being spoken.  This is an incredible and miraculous event. 

Another reason I believe Luke mentions all these different people groups and nations here is to show that God is a missional God and that His message is for all peoples.  Notice Luke says that there were devout men from every nation under heaven represented.  Then he says that they all heard the message of Jesus’ disciples—the message of the mighty works of God in their own language. 

We see here in Acts 2, like we do throughout the book of Acts and throughout the Bible, that God is a missional God.  He is a God who desires to be known where He is not known—by all peoples everywhere.  He wants to be known by Jews all throughout the known world (Acts 2) and also by Samaritans (Acts 8) and Gentiles (Acts 10).  By those who are far off and followers of no one and by those who are nearby and followers of the wrong ones.  He wants to be known by the godless and the misguided—by the uninformed and the misinformed.  He wants to be known and worshiped where He is not known and worshiped—by all peoples everywhere.