“And they were all filled with the Holy Spirit and began to speak in other tongues as the Spirit gave them utterance.” (Acts 2:4)
On the Day of Pentecost the disciples of Jesus first began to preach the gospel to others. They were able to preach with great boldness and exuberance only because they were filled by the Holy Spirit whom Jesus had promised to send them. And He was poured out on that day with such great fanfare and intense fervor that thousands of people were attracted to come and hear what the disciples were saying. The Holy Spirit was enabling each of those disciples to speak in languages they did not know to people who did, Jews who were in Jerusalem from other parts of the Roman Empire, all gathered for the harvest feast of First Fruits. And the first fruits gathered in the church that day were those nearly 3000 people believed in Jesus and were baptized.
Most of us realize that on Pentecost one of the great manifestations of the Holy Spirit was this miraculous speaking in tongues. This was evidence of the presence of the Holy Spirit but also signified that the Lord had begun the reversal of the curse of Babel (Genesis 11), the curse of human alienation, prejudice and disharmony. At Babel humans came together to achieve glory for themselves in man made religion and works of the flesh, all apart form God. Now in the Church the Lord was bringing together people from all nations and languages. Now in Christ all can be one once again united by the Holy Spirit and a common faith, not by their own works not by their own religious efforts, but by the work of Jesus on the cross.