The day of Pentecost is typically associated with stupendous signs and miracles. Acts 2 records that when the Holy Spirit was given, the display of ability and power astounded everyone present. There was a sound like a mighty rushing wind (verse 2). It appeared that fire rested on the apostles (verse 3), and when they spoke, every person present could hear what was being said in his own language, even his own dialect (verses 4-11).
Because of the brief description given in Acts 2, various religious denominations have sprung up which practice speaking in gibberish—which the disciples definitely were not doing—and being "slain in the Spirit," which is clearly not a biblical concept. These sincere but misled people focus on miracles and manifestations as "proof" that they have received the Holy Spirit. Every week they gather to "pray down" the Spirit—or at least a spirit—for their own use and gratification. The focus of their meetings is on the experience rather than on instruction, admonition, rebuke, or encouragement (see II Timothy 3:16).
Before this event in Acts, Jesus Himself explained to His disciples the importance of their receiving the Holy Spirit, as well as what signs would be shown as a result (Acts 1:4-9). The very last thing the resurrected Christ said before He ascended to the Father was, to paraphrase, "You will receive power when you receive the Holy Spirit, and this will enable you to be witnesses of Me." Through the giving of the Holy Spirit, Christ's disciples would have the necessary means to be lights to the world and to demonstrate a way to live that glorified God.
David C. Grabbe
The Pentecost Witness
Those in the house were filled with the Holy Spirit, and they spoke with other languages. These were not unknown languages, but languages familiar to people in the area, as Acts 2:6 shows.
John W. Ritenbaugh
Pentecost and the Holy Spirit
God's Holy Spirit imparts to us His love, giving us the power to obey His laws in their full spiritual intent. The repentant sinner is then a changed person - his whole outlook and purpose is changed as he is led by the Spirit.
Earl L. Henn (1934-1997)
Basic Doctrines: Salvation