Pentecost Sunday is the Christian festival celebrating the descent of the Holy Spirit on Jesus' disciples after his ascension. The occasion is named as such as it is marked on the seventh Sunday after Easter or 50 days from Easter Sunday (from the Greek word "pentekoste" or "fiftieth").
This year, the occasion falls on June 4. Pentecost is a special day for Pentecostals, being the most ardent followers of the Holy Spirit. It also considered as the birth of Christianity for it is the day when Jesus' followers began the Great Commission of making disciples of all nations (Matthew 18:19-20).
Pentecost is an occasion when Christians are thankful for the Holy Spirit's moving in God's work. To recall, after Jesus' resurrection and ascension to heaven, the apostles were left behind not knowing what to do. They were a small number of believers without a leader and were alone and afraid.
This changed when the Holy Ghost descended upon them. Being baptized with the Spirit emboldened them to preach the Gospel even if it cost their lives. This kind of courage, passion and commitment can only be manifested with the Holy Spirit's anointing and it does show in the way Pentecostals and Evangelicals worship.
The greatest proof of the Holy Spirit's work can be seen in the stature of Christianity as the largest religion in the world. It is the fastest growing religion in countries where it is a minority. Its influence can be seen in the growing churches, worldwide ministries, televised programs with a global audience and conversions to the faith.
How can this be possible? The Holy Ghost bestows seven gifts namely wisdom, understanding, counsel, fortitude, knowledge, piety and fear of the Lord — spiritual tools needed to become a witness for Jesus to the ends of the earth (Acts 1:8).