When the Day of Pentecost had fully come, they were all with one accord in one place. 2 And suddenly there came a sound from heaven, as of a rushing mighty wind, and it filled the whole house where they were sitting. 3 Then there appeared to them divided tongues, as of fire, and one sat upon each of them. 4 And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance.
Today is Pentecost Sunday, Pentecost being one of the major feast celebrations for Israel. But after what is recorded taking place in Acts 2:1-4 Pentecost became significant to all believers for it was the church age along with the Grace dispensation. For it was on this day that the promise of Christ and the prophet Joel was fulfilled and the Holy Spirit all that were gathered together as believers.
Many think this promise was for early church and not for today, and then others believe that you get fullness of the Holy Spirit when you get saved. But as Pentecostals we believe that the Baptism of the Holy Spirit is subsequent to salvation. When we get saved we receive the Spirit of adoption whereby we relate to God as Father (Romans 8:15) But the Baptism of the Holy Spirit is an experience that endues us with power for service and operation in the gifts of the Spirit.