Pentecost (also called Trinity Day or Descent of the Holy Spirit) is one of the Great Feasts of the Orthodox Church, celebrated fifty days after Pascha (thus always falling on a Sunday, this year: June 19, 2016, next year: June 4, 2017, and May 27, 2018, the year after that.)
Day of Pentecost
Fifty days after the Resurrection, on the excising Jewish feast of Pentecost, while the disciples and many other followers of Jesus Christ were gathered together to pray, the Holy Spirit descended upon them in the form of "cloven tongues of fire," with the sound of a mighty rushing wind, and they began to speak in languages that they did not know. There were many visitors from the Jewish diaspora to Jerusalem at that time for the Jewish observance of the feast, and they were astonished to hear these untaught fisherman speaking praises to God in their alien tongues. This account is detailed in the Acts of the Apostles, chapter 2.
The number fifty, as in the fiftieth day after Pascha, stands for eternal and heavenly fulfillment, seven times seven, plus one.
Feast of Pentecost
The Orthodox Church sees Pentecost as 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 his Church. It is traditionally called the beginning of the One Holy Catholic and Apostolic Church.
Besides celebrating the coming of the Holy Spirit, the feast also celebrates the full revelation of the divine Trinity, Father, Son, and Holy Spirit. Hymns of the Church, celebrate the sign of the final act of God's self-disclosure to the world of His creation.
To Orthodox Christians, the feast of Pentecost is not just a celebration of an event in history. It is also a celebration their membership in the Church. They have lived Pentecost and received "the seal of the gift of the Holy Spirit" in the sacrament of chrismation.
Celebration of the feast
Three angelic figures who appeared to Abraham
For the feast of Pentecost the icon of the Holy Trinity, the three angelic figures who appeared to Abraham, is placed in the center of the church for veneration. This icon is used with the traditional Pentecost icon. The church building is decorated with flowers and the green leaves of the summer to show that God's divine breath comes to renew all creation. Green vestments and coverings are also used.
In many parishes the feast is celebrated starting the evening before with Great Vespers. Some parishes also serve Matins on the morning of the feast before the Divine Liturgy.
The Liturgy of Saint John Chrysostom with special hymns replacing the standard Antiphons. The hymns O Heavenly King and We have seen the True Light are sung for the first time since Easter, calling the Holy Spirit to "come and abide in us," and proclaiming that "we have received the heavenly Spirit."
An extraordinary service called the Kneeling Vespers, is observed on the evening of Pentecost. This is a Vespers service to which are added three sets of long poetical prayers, the composition of Saint Basil the Great, during which everyone makes a full prostration, touching their foreheads to the floor (prostrations in church having been forbidden from the day of Pascha (Easter) up to this point). In many parishes, this service is done immediately after the Liturgy.
The Ecumenical Patriarch in Constantinople reads kneeling
the prayers of kneeling (photo from here)
The Monday after Pentecost is the Feast of the Holy Spirit in the Orthodox Church, and the Sunday after Pentecost is the Feast of All Saints.
Even though the start of the Church year is considered to start in September, the liturgical center of the annual cycle of Orthodox worship is the feast of Pascha, preceded by Great Lent, and pre-lent, and followed by the fifty days of paschal celebration until the feast of Pentecost. Until the start of the next Great Lent, the Sundays and weeks following Pentecost, are numbered from Pentecost. Liturgical readings and hymns will be based on the "weeks after Pentecost" as listed in the Octoechos, Apostolos, and Lectionary arranged Gospel.
The holy icon of All Saints, from the article
Theosis (deification): The True Purpose of Human Life
Troparion (Tone 8) 
Blessed art You O Christ Our GodYou have revealed the fishermen as most wiseBy sending down upon them the Holy SpiritThrough them You drew the world into Your netO Lover of Man, Glory to You!
Kontakion (Tone 8)
When the most High came down and confused the tongues,He divided the nations;But when he distributed the tongues of fireHe called all to unity.Therefore, with one voice, we glorify the All-holy Spirit! See also
Pentecost icon (from here)
Holy Pentecost (from here)
The Pentecost icon depicts the descent of the Holy Spirit onto the Church. It is usually displayed for veneration, at the center of the church, on the Sunday of Pentecost.
The icon has the Apostles sitting, as on Mount Sion, representing the first Church community, the beginning of the Christian Church. They form a semicircle to express the unity of the Church, the Mystical Body of Christ. The icon is not a depiction of the historical events of Pentecost, but it signifies that this is a great event for all time.
As with many icons, the Apostles are pictured in an inverse perspective, the figures grow larger as they recede into the background. Also, the building that the Apostles were in, is shown as background.
The Holy Spirit
At the top of the icon is another semicircle, with rays coming from it. The rays are pointing toward the Apostles, and the "tongues of fire" are seen descending upon each one of them signifying the descent of the Holy Spirit.
At the center of the group of Apostles, there is a place which is unoccupied. It is reserved for Christ, the invisible head of the Church. Some ancient icons symbolize Christ's invisible presence with an altar, the throne of His glory. Clearly, no one else can be depicted here.
The Apostles sit orderly, unlike the Ascension icon where they seem confused. This is to show the gift of the Holy Spirit, the inner life of grace. The gift to the Church.
The group of twelve represent the Church, not just those mentioned in the book of Acts as being with the others on the day of Pentecost. Pictured in the icon is Paul, who became an Apostle of the Church and the greatest missionary. The four Evangelists, Matthew, Mark, Luke, and John, are shown holding the not yet written books of the Gospel. Other Apostles are holding scrolls that represent the teaching authority given to them by Christ.
In yet another semicircle, at the bottom of the icon, is a symbolic figure of a king. He is in a dark place that represents the world enveloped by sin. This one person represents the whole world that had formerly been without the light of faith. He is bent over to show he was made old by the sin of Adam. Through the power of the Holy Spirit the Church brings light to the whole world by her teaching. Sometimes, the figure is shown coming out, into the light, having a cloth containing scrolls which represent the teaching of the Apostles.
Feast of Holy Pentecost
Quotes about Pentecost - Orthodox Church Quotes website
Holy Pentecost Father Alexander Schmemann
How to Celebrate Pentecost at Home by Fr. Anthony M. Coniaris (excerpt from Making God Real in the Orthodox Christian Home)
Icons of the Descent of the Holy Spirit (Pentecost)
Photo from the Pentecost feast's celebration 2015
at the Orthodox Diocese of Burundi and Rwanda (from here)
How to Celebrate Pentecost at Home (from here)
Fr. Anthony Coniaris' Making God Real in the Orthodox Christian Home offers us many ways to enrich the lives of our families. The following section deals with the Feast of Pentecost.
by Fr. Anthony Coniaris
Since Pentecost is the birthday of the Church it can be celebrated in the home by baking a special birthday cake for the Church and serving it as dessert. One candle may be used to represent each 100 years of the Church's existence. Nineteen or twenty candles may be used. The whole family can sing "Happy Birthday" to the Church and blow the candles out together.
The opportunity may be used to read and discuss the Scripture lessons that are read in Church on Pentecost (Acts 2:1-11 and John 7:37-52, 8:12).
A discussion can follow on what the Church is. It is the Body of Christ through which He continues to be present in the world today: to teach us, forgive us, guide us, bless us, strengthen us. After Christ ascended into heaven, He established the Church to carry on His work. When we go to Church on Sunday, we are going to Christ. When we support the Church with our offerings, we are supporting Christ. When we listen to the Church, we are listening to Christ.
The Body of Christ
The Church is called the Body of Christ because just as Christ once used His physical Body to do the work of God in the world, so now He uses His mystical Body, the Church.
On the long high front wall of a church that was just being completed, an artist started painting a picture of Christ as the Good Shepherd. Only the firm brush strokes outlining the head could be seen. A stranger stopped in and asked curiously, "When will the picture be finished?"
A workman replied. ''That picture? It is finished.''
"Finished?" repeated the startled visitor. "Why all it is, is the outline of a head. Most of it is still missing - the eyes, mouth, arms, legs and feet - the whole body is missing!"
"You won't see that on a wall," the workman replied. "The body of Christ is the congregation of people who will be worshipping in this church. The Body of Christ is the Church."
St. Paul writes, "He (Christ) is the head of the body, the Church" (Col. 1:18). St. [John] Chrysostom said, "Christ is the head of the body, but what can the head do without hands, without feet, without eyes, without ears, without a mouth?"
As the Head of the Body, Christ issues orders to the various members. He is the brain; the One in Whom all the fullness of God dwells bodily. What a privilege God bestows on us when He ties us so intimately with Christ and with each other as to make us constitute one Body with Him as the Head. When we meditate on this analogy, we come to look at prayer as the members of the Body (the Church) reporting for duty to the Head (Christ). He continues to be present in the world today.
The Holy Spirit
Finally, parents may explain that Pentecost is the day on which the Holy Spirit came to us in His fullness. On this day we kneel three times during the church service as we pray together with the priest that the same Holy Spirit Who filled the first apostles with God's presence and power may fill us today with the same power that we may experience the reality of God in our lives.
The Holy Spirit must be constantly attained. He should be received daily. To achieve this, it is necessary to wait prayerfully and expectantly for Him as the apostles did before Pentecost. "All these with one accord devoted themselves to prayer..." (Acts 1:14). This kind of prayerful waiting is essential if we are to receive the Holy Spirit.
St. Seraphim of Sarov describes the whole purpose of the Christian life as nothing more than the receiving of the Holy Spirit:
"Prayer, fasting, vigils and all other Christian acts, however good they may be in themselves, certainly do not constitute the aim of our Christian life; they are but the indispensable means of attaining that aim. For the true aim of the Christian life is the acquisition of the Holy Spirit of God. As for fasts, vigils, prayer and almsgiving, and other good works done in the name of Christ, they are only the means of acquiring the Holy Spirit of God... [Ed. Note: emphasis mine]. Prayer is always possible for everyone, rich and poor, noble and simple, strong and weak, healthy and suffering, righteous and sinful. Great is the power of prayer; most of all does it bring the Spirit of God and easiest of all is it to exercise."St. Seraphim of Sarov
It has been said that St. Seraphim in the above words sums up the whole spiritual tradition of the Orthodox Church. For, what is greater than to possess the Holy Spirit? And what is easier than the means by which He comes to us: prayer?
No prayer is complete unless it includes a petition to the Holy Spirit that He come to dwell in us. Thus, through prayer every day becomes Pentecost.
This would be a good time to teach your children one of the best known and most used prayers of the Orthodox Church. Almost every one of our church services begins with it. It is a prayer to the Holy Spirit and should be used often in your family devotions:
O Heavenly King, the Comforter, the Spirit of Truth, Who are everywhere present and fills all things, Treasury of good gifts and Giver of Life, come and abide in us, and cleanse us of all impurity, and save our souls, 0 Good One.[Ed. Note: In the Scriptures, Jesus tells His Disciples that He must leave so that the Spirit, the Comforter, can come. This is lived out in the Orthodox Church in the following way: this prayer is not recited between the Feasts of Pascha and Pentecost as we await the coming of the Holy Spirit on Pentecost.]
Copies of Making God Real in the Orthodox Christian Home can be purchased from Light & Life Publishing for $10.95 SH. 4818 Park Glen Rd., Minneapolis, MN 55416 / 612-925-3888 / FAX 888-925-3918 / Web site: http://www.light-n-life.com. Excerpt reprinted with permission.
© 1998 by Orthodox Family Life and the original author(s).
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