Ten days after the ascension of Christ and fifty days after his resurrection, the Holy Spirit descended on the disciples on the day of Pentecost. In the first century, Pentecost was already an established Jewish festival also known as the Feast of Weeks, which drew people from many nations back to Jerusalem (Lev. 23:15-21; Deut. 16:16). Pentecost symbolizes a new beginning.
“In celebrating Pentecost, the church: expresses gratitude for Christ fulfilling his promise to send “another counselor” (John 14:16), celebrates the work of the Spirit in renewing all of creation, professes confidence in the Spirit’s power for its mission, and grows in awareness of its calling to reach the world with the gospel.”