Before Jesus returned to the Father in Heaven he promised to send the Holy Spirit. The disciples waited in Jerusalem and on the day of Pentecost the Lord Jesus Christ fulfilled his promise – he sent the Holy Spirit.

"When the day of Pentecost came, they were all together in one place. Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. They saw what seemed to be tongues of fire that separated and came to rest on each of them. All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them. Now there were staying in Jerusalem God-fearing Jews from every nation under heaven. When they heard this sound, a crowd came together in bewilderment, because each one heard them speaking in his own language. Utterly amazed, they asked: "Are not all these men who are speaking Galileans? Then how is it that each of us hears them in his own native language? Parthians, Medes and Elamites; residents of Mesopotamia, Judea and Cappadocia, Pontus and Asia, Phrygia and Pamphylia, Egypt and the parts of Libya near Cyrene; visitors from Rome (both Jews and converts to Judaism); Cretans and Arabs--we hear them declaring the wonders of God in our own tongues!" (Acts 2:1-11)

One of the manifestations of the Holy Spirit was 'the gift of tongues', or the ability to speak in other languages, which he gave to the disciples. It was this phenomenon that prompted those who heard the disciples to ask, 'how is it that each of us hears them in his own native language?' These people had come to Jerusalem from many parts of the world and were amazed that these Galileans could speak their languages.

In answering their question Peter explained that the Holy Spirit gave them this gift, this ability to speak other languages.

To help us understand what happened, let us imagine going to India today and meeting with people from all over that country. Dozens of different languages are spoken among those who have gathered: Hindi, Telagu, Malayalam, etc. Communication is not a problem to you because the Holy Spirit has given you a gift to enable you speak in the languages of those people present. That is what happened on the day of Pentecost.

When the Bible speaks about 'the gift of tongues,' it is referring to a gift given by the Holy Spirit that enabled people to speak in other languages.

Why did the Lord give this gift? What purpose did it serve? The Bible says, 'Tongues then, are a sign, not for believers, but for unbelievers.' (1 Corinthians 14:22).Tongues were for the benefit of the unbeliever, providing him with evidence to help him become a believer.