“…the fiftieth day stands as the beginning of the era which is beyond the limitations of this world, fifty being that number which stands for eternal and heavenly fulfillment in Jewish and 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 the day of the final and perfect end (in Greek eschaton means the end). For when the Messiah comes and the Lord’s Day 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 which was preached on the first Sunday of Pentecost (Acts 2: 1 7; Joel 2: 28-32).
“Once again it must be noted that the feast of Pentecost is not simply the celebration of an event which took place centuries ago. It is the celebration of what must happen and does happen to us in the Church today. We all have died and risen with the Messiah-King, and we all have received his Most Holy Spirit. We are the “temples of the Holy Spirit.” God’s Spirit dwells in us (Rom 8; 1 Cor 2-3, 12; 2 Cor 3; Gal 5; Eph 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.”
Read the whole article here: Pentecost: The Descent of the Holy Spirit