What does Acts 2:8 mean?

At the time of Jesus' earthly ministry, the residential population of Jerusalem is thought to be about 100,000. The Jewish calendar includes three feasts—Passover, Pentecost, and the Feast of Tabernacles—which all Jewish men are to try to celebrate in Jerusalem. On those occasions, the population of Jerusalem swells to about a million people. This is why Jesus and the disciples slept on the Mount of Olives, outside the city, during the Passover (Luke 21:37).

These Jews and proselytes come from all over the Roman Empire including Africa, modern-day Asia Minor, modern-day Iran and Iraq, and Italy (Acts 2:9–11). Those from west of Judea probably all speak Greek and those from the east probably all speak some variant of Aramaic. But they most likely also have a local language they grew up with. So they are amazed to hear uneducated Galileans speaking those local dialects.

The understanding of what "speaking in tongues" means is a controversial topic today. Many think it is a special language that only God can understand. Passages like 1 Corinthians 14:2 seem to say speaking tongues is uttering "mysteries in the Spirit." This passage is clear that when someone is inspired by the Holy Spirit to speak in tongues, they are speaking an established, earthly language. First Corinthians 14:22 says, "tongues are a sign not for believers but for unbelievers." So, tongues-speaking is for sharing the gospel and speaking God's truth to people who use that language.

This verse exemplifies the principle of the accommodation of God. In laymen's terms, it means "He meets us where we are." He knows we are "but dust and ashes" (Genesis 18:27). He is infinite and His ways and thoughts are higher than we could ever reach (Isaiah 55:9). Like a parent who teaches her child to read using simple children's books, God speaks to us in ways we can more easily understand. Here, God doesn't force the varied audience to hear the gospel in Greek or Aramaic, which may be their second or third language. He reaches them at their most personal level, showing them that the gospel is for them in their culture and in their homes. In addition, the miracle of the disciples using tongues validates their message as having come from God.