The day of Pentecost, fifty days after the resurrection of Jesus from the dead, celebrates the coming of the Holy Spirit and the calling of the church by the Spirit of the Risen One.
“When the day of Pentecost arrived, they were all together in one place. And suddenly there came from heaven a sound like a mighty rushing wind, and it filled the entire house where they were sitting. And divided tongues as of fire appeared to them and rested on each one of them. 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.” And all were amazed . . .”
Acts 2:1–12a
If you go back to the Old Testament, you will discover that Pentecost was one of the Jewish feast days. They didn't call it Pentecost, that's the Greek name. They called it Shavout or the Feast of Weeks (or Harvest). It’s mentioned five places in the first five books of the Bible — Exodus 23 and 24, Leviticus 16, Numbers 28, and Deuteronomy 16.
This feast was a great celebration of God bringing about the harvest to provide for his people. Eventually, this celebration turned into a pilgrimage festival with the Jewish people traveling to Jerusalem to celebrate. This was a grand celebration. The streets of Jerusalem would have been filled with thousands of pilgrims who had come from all over the land to celebrate the goodness of God and the bringing in of the wheat harvest. This is why there were a variety of languages being spoken when the Holy Spirit descended upon the people—because the people gathered together were from various locations outside of Jerusalem. They were in Jerusalem to celebrate Shavout/Pentecost.
The miracle that occurs here is that people, because of the power of the Holy Spirit, could understand the various languages!
Pentecost is still important for us today because it represents the beginning of the Christian Church. It reminds us that Jesus' promise that God would send the Holy Spirit was fulfilled. And just as God brought the harvest of wheat as a provision for his people, he will bring about the harvest of his people to be the Church.