One of the most frequently used prayers of the Orthodox Church is:
O Heavenly King, the Comforter, the Spirit of Truth, who art everywhere and fillest all things. Treasury of blessings and Giver of Life, come and abide in us and cleanse us from every impurity, and save our souls, O Good One.
Most Orthodox services begin with this prayer. But interestingly enough, it is not prayed from Pascha (Easter) to Pentecost. Easter, of course, is the Resurrection of Jesus Christ. Forty days later the feast of Ascension, which commemorates Christ’s Ascension into heaven. Fifty days after Easter is Pentecost (Pentecost means fifty in Greek). As during His earthly ministry Jesus Christ prophesied the coming of the Holy Spirit at Pentecost (John 7: 37-19):
On the last day of the feast, the great day, Jesus stood up and proclaimed, “If any one thirst, let him come to me and drink. He who believes in me, as the scripture has said, `Out of his heart shall flow rivers of living water.'” Now this he said about the Spirit, which those who believed in him were to receive; for as yet the Spirit had not been given, because Jesus was not yet glorified.
In other words, the Holy Spirit would not be given until after Christ had been glorified, i.e., until Christ had risen from the dead. Christ is predicting the coming of the Holy Spirit fifty days after His resurrection. As mentioned above, Pentecost is the Greek word for fifty. Originally it was a Jewish feast day. It was the fiftieth day after Passover. In the Greek Old Testament it is called the “Feast of Weeks”. In Judaism Pentecost was a harvest festival. It was celebrated seven weeks after the beginning of the wheat harvest. On Pentecost, the first fruits of the harvest were offered in the temple of Jerusalem as a thanksgiving to God for a successful harvest. After the Romans destroyed Jerusalem and the Temple the first fruits could no longer be offered in the Temple, so that Pentecost was celebrated as the giving of the new law to Moses on Mount Sinai.
In the New Testament in the book of Acts we see Pentecost described. Present were the twelve Apostles (after Judas had betrayed Christ Matthias was elected to take his place). Also present were the 120disciples and Mary, the Mother of God. It is described in Acts 2:1-5:
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 and resting on each one of them. And they were all filled with the Holy Spirit and began to speak in other tongues, as the Spirit gave them utterance. Now there were dwelling in Jerusalem Jews, devout men from every nation under heaven.
Tradition tells us that this took place in the Upper Room on Mount Sinai where Jesus had celebrated the Last Supper with his disciples. Further on we see that St. Peter and the other Apostles began to preach in various languages they had never spoken before so that people from any different places heard the Apostles preaching in their own language. This is the true “speaking in tongues”. In modern Christianity there are some Christians who speak in tongues. However, they are saying meaningless syllables. This is different from the true speaking in tongues at Pentecost. Some people thought the Apostles were drunk but St. Peter told the crowd that they were not drunk but filled with the Holy Spirit. He tells the people that the words of the prophet Joel were being fulfilled:
“And it shall come to pass afterward, that I will pour out my spirit on all flesh; your sons and your daughters shall prophesy, your old men shall dream dreams, and your young men shall see visions.” (Joel 2:28)
St. Peter preached that Jesus Christ was the Messiah promised in the Old Testament.
The crowd was so impressed with the preaching of St. Peter that about 3000 people accepted faith in Jesus and were baptized. Pentecost is the birthday of the Church.