Acts 2:1-4 (NIV)
When the day of Pentecost came, they (the apostles) 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[or languages] as the Spirit enabled them.
Acts 2:32-33 (NIV)
(Peter said to the crowd) “God has raised this Jesus to life, and we are all witnesses of the fact. Exalted to the right hand of God, he has received from the Father the promised Holy Spirit and has poured out what you now see and hear.”
Ephesians 1:13-14 (NIV)
And you also were included in Christ when you heard the word of truth, the gospel of your salvation. Having believed, you were marked in him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance until the redemption of those who are God’s possession—to the praise of his glory.