Celebrated fifty days after Passover (Exodus 12:24-28) and the Feast of Unleavened Bread, Pentecost (also called the Feast of Weeks, Leviticus 23:15-16) commemorated the giving of the law on Mount Sinai. Following the death, resurrection, and ascension of Jesus Christ, Pentecost Sunday was given a new meaning with the fulfillment of the promise of Jesus to send another Counselor or Helper (John 14:15-26). Just as the giving of the law tangibly demonstrated God’s active presence with the Israelites, even more the giving of His Holy Spirit poured out on those who believe remind us that He is still Immanuel: God with us.
When the day of Pentecost arrived, they were all together in one place. 2 And suddenly there came from heaven a sound like a mighty rushing wind, and it filled the entire house where they were sitting. 3 And divided tongues as of fire appeared to them and rested on each one of them. 4 And they were all filled with the Holy Spirit and began to speak in other tongues as the Spirit gave them utterance. (Acts 2:1-21)
The impact of the outpouring of the Holy Spirit was immediate! Read all about it in Acts 2:1-21 and marvel that the very same Holy Spirit seals and empowers those who are in Christ even today (Ephesians 1:13-14).
To learn more about the day of Pentecost, you can watch this video from The Bible Project.