The Old Testament feast of Pentecost occurred 50 days after Passover—the commemoration of the Exodus of the Israelites from captivity and slavery in Egypt—in celebration of God’s gift of the Ten Commandments to Moses on Mount Sinai.In the New Covenant of the Messiah, the Passover event takes on its new meaning—the celebration of Christ’s Resurrection, the “passing over” from death to life and from earth to heaven, the “exodus” of God’s People from this sinful world to the eternal Kingdom. The New Testament Pentecost also is fulfilled and made new by the coming of the “new law” with the descent of the Holy Spirit upon the disciples of Christ. As we read in the Acts of the Apostles 2:1-4, “When the day of Pentecost had come, they were all together in one place. And suddenly a sound came from heaven like the rush of a mighty wind, and it filled all the house where they were sitting. And there appeared to them tongues as of fire, distributed as resting upon each one of them. And they were all filled with the Holy Spirit.” The Holy Spirit Christ promised to His disciples came on the day of Pentecost (John 14:26, 15:26; Luke 24:49; Acts 1:5) as the apostles received “the power from on high” and began to preach and bear witness to Jesus as the risen Christ, the King and the Lord. Traditionally, this moment has been called the “birthday of the Church.”In the liturgical services for the Great Feast of Pentecost, the coming of the Holy Spirit is celebrated together with the full revelation of the Holy Trinity: Father, Son, and Holy Spirit. The fullness of the Godhead is manifested with the Spirit’s coming to man, and the Church’s hymns celebrate this manifestation as the final act of God’s self-disclosure and self-donation to the world of His creation. For this reason, Pentecost Sunday also is called Trinity Day in the Orthodox Christian tradition. On this day, the icon of the Holy Trinity — particularly that of the three angelic figures who appeared to Abraham, the forefather of the Christian faith—often is placed in the center of the church, alongside the traditional Pentecost icon depicting the tongues of fire hovering over the Theotokos and the 12 Apostles, the original prototype of the Church, who sit in unity surrounding a symbolic image of “cosmos,” the world.On Pentecost, we have the final fulfillment of the mission of Jesus Christ and the first beginning of the messianic age of the Kingdom of God mystically present in this world in the Church of the Messiah. For this reason the 50th day stands as the beginning of the era that is beyond the limitations of this world, 50 being that number which stands for eternal and heavenly fulfillment in Jewish as well as Christian mystical piety: seven times seven, plus one.Thus, Pentecost is called an “apocalyptic day,” which means the day of final revelation. It is also called an “eschatological day,” which means that it is the day of the final and perfect end—in Greek, the eschaton. When the Messiah comes and the Day of the Lord is at hand, the “last days” are inaugurated, in which “God declares, ‘I will pour out my Spirit upon all flesh.’” This is the ancient prophecy to which the Apostle Peter refers in the first sermon of the Christian Church, preached on that first Pentecost Sunday (Acts 2: 1 7; Joel 2: 28-32).The Great Feast of Pentecost is not simply the celebration of an event which took place centuries ago. Rather, it is the celebration of what must happen—and indeed does happen—to us in the Church today. We have died and risen with the Messiah-King, and we have received His Most Holy Spirit. We are the “temples of the Holy Spirit.” God’s Spirit dwells in us (Romans 8; 1 Corinthians 2-3, 12; 2 Corinthians 3; Galatians 5; Ephesians 2-3). We, by our own membership in the Church, have received “the Seal of the Gift of the Holy Spirit” in the sacrament of Chrismation. Pentecost has happened to us.During the Divine Liturgy on Pentecost, we recall our baptism into Christ as we sing, in place of the Trisagion, the well known verse from Galatians: “As many as have been baptized into Christ, have put on Christ.” The usual antiphons are replaced by special psalm verses that emphasize the meaning of the feast, while the day’s readings from the Epistles and Gospels recall the Holy Spirit’s coming to men. The kontakion speaks of the reversal of Babel, as God unites the nations into the unity of His Spirit. And the troparion proclaims the gathering of the entire universe into God’s “net” through the work of the inspired apostles. In the hymns “O Heavenly King” and “We have seen the True Light”—sung on Pentecost for the first time since Holy Pascha—we invoke the Holy Spirit to “come and abide in us” while proclaiming that “we have received the heavenly Spirit.”On the evening of Pentecost Sunday, at Vespers, three lengthy prayers are recited, during which we kneel for the first time since Pascha. The Monday after Pentecost is the Feast of the Holy Spirit, while the Sunday after Pentecost is the Feast of All Saints. This is the logical liturgical sequence, since the coming of the Holy Spirit is fulfilled in us as we pursue holiness and sanctity in our own lives—that holiness and sanctity which constitute the very purpose of the creation and salvation of the world: “Thus says the Lord: ‘Consecrate yourselves therefore, and be holy, for I your God am holy’” (Leviticus 11:44-45, 1 Peter 1:15-16).Thus, Pentecost ushers in a new era, in which we are called to pursue sainthood by acquiring the Holy Spirit, by opening ourselves to the fullness of Christ’s revelation to mankind, and by anticipating the Kingdom of God, yet to be fully revealed, but already fully present in our midst as we entreat the Holy Spirit to “come and abide in us” now and in the life of the world to come.