Jesus and Pentecost:

In Acts 1, just before the resurrected Jesus is taken up into heaven, he tells the disciples about the Father's promised gift of the Holy Spirit, which will soon be given to them in the form of a powerful baptism. He tells them to wait in Jerusalem until they receive the gift of the Holy Spirit, which will empower them to go out into the world and be his witnesses.

A few days later, on the Day of Pentecost, the disciples are all together when the sound of a mighty wind comes down from heaven, with tongues of fire resting on them. The Bible says, "All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them." The crowds observed this event and heard them speaking in different languages. They were amazed and thought the disciples were drunk on wine. Then Peter got up and preached the Good News of the kingdom and 3000 people accepted
[link to christianity.about.com]