What does the Bible say about the Holy Spirit and Pentecost?

Acts 2 details the day of Pentecost as a significant moment when the Holy Spirit filled the apostles, allowing them to speak in various languages as a sign of God’s power. This event fulfilled the prophecy of John the Baptist, who stated that Jesus would baptize with the Holy Ghost and fire. Thus, Pentecost marks the inauguration of the Church’s new era filled with the Spirit, where believers have direct access to God’s presence, reflecting the significant transition from the Old Covenant to the New.