On the tenth day after the Ascension of Jesus Christ during the Jewish feast of Pentecost, at the third hour, but according to our reckoning at nine o’clock in the morning, when people usually go to the temple both for offering up a sacrifice and prayer  all the disciples were assembled in Jerusalem, in the upper room (Acts 1:13), which was «on Mount Zion», «and suddenly there came a sound from heaven, as of a rushing mighty wind,» (as though from an unusually strong wind).»
Actually there was no wind rustling, but the noise was similar as if it were from the strength of a wind, but without the wind.» This noise «filled the whole house where they were sitting», – not only of the apostles, but, according to the commentary of St. John Chrysostom, even other believers in Christ (Acts 1:16).
In that instant in the middle of the house in the air appeared many tongues as of fire, being carried above the heads of the disciples, dropped down and rested on them. They were not really fiery tongues, but were «as if As fast as the Divine Fire flared up in the souls of the believers, they were filled with holy ecstasy and in reply to the gift of Heaven have lifted up to Heaven a word of praise and thanksgiving to the Great God for the benefactions to the human race. And they all «began to speak with other tongues, as the Spirit gave them utterance»: each of these gifted ones began to speak in whatever language even if the other language was unknown to him, in the language of a country where he never lived or a language which he never studied; the knowledge of this language for him was exclusively a gift of the Holy Spirit; and the power of the Holy Spirit first of all was found out by their ability in languages, because this ability first of all was necessary for the apostles, so that they could preach the Gospel message all over the world.
Meanwhile the stormy noise of the breath from Heaven attracted many Jews to the apostolic quarters. Seeing the people gathering for them, believers with praises and hymns on their lips they went on the flat roof of a house where they were; for it is natural to assume that they were filled with holy joy, the desire and zeal to announce the glory of God revealed in them to other people. They spoke about «wonderful works of God» (Acts 2:11), which now opened for them in all the fullness and light; they praised the omnipotence, mercy and wisdom of God, they magnified the Lord Jesus, they confessed that He is the Christ announced by the ancient prophets, the Redeemer of our sins, that He is risen and, ascended with glory into Heaven to the Father, who sent the Holy Spirit, who teaches all wisdom, and finally, they thanked God for everything that they have received through grace from Christ.
Hearing these words of praise and thanksgiving, all those gathered in the apostolic quarters were amazed by the new unexpected. But the impious were also found, who began to swear at the God-inspired preachers . Then the Holy Apostle Peter raised his voice and delivered his first sermon, in which he pointed out the glorious events accomplished in this day, the fulfillment of ancient prophesies and the completion of the great work of salvation of the people, which was fulfilled on earth by the crucified and resurrected Lord Jesus Christ.
This first Christian sermon was simple and brief, but since the Holy Spirit spoke through the mouth of the Holy Apostle Peter, his words penetrated the hearts of the hearers and won over their obstinacy. «Now when they heard this, they were cut to the heart, and said to Peter and the rest of the apostles, ‘Men and brethren, what shall we do?’ (Acts 2:37). «Repent», the Holy Apostle Peter answered them, «and let every one of you be baptized in the name of Jesus Christ» and you will not only be forgiven; but you shall also «receive the gift of the Holy Spirit». For the promise of the Holy Spirit is given» Then those who gladly received his word» that is of the Apostle Peter immediately repented, believed, and were baptized (Acts 2:41), and the new Church has grown from 120 (Acts 1:15) to 3000 men.
Thus ended the events, now celebrated, have ended in the complete celebration of the Holy Spirit over the unbelievers. In memory of this wonderful and glorious event we refer to this day as the day of the Descent of the Holy Spirit on the Apostles .
This feast is still called Trinity Day; because the appearance of the Holy Spirit has revealed to the people in a very clear light, how necessary the mystery of the Holy Trinity was for them; and therefore even for the Holy Church, teaching us «in an Orthodox way» and piously to confess the All-holy Trinity, for in its prayers and hymns for this day it honors and praises all three Persons of the Holy Trinity, who participated in the descent of the Holy Spirit: God the Father, who sent the Holy Spirit, God the Son Jesus Christ, who entreats the Father to send the Holy Spirit, and God the Holy Spirit, who descended appearing as fiery tongues.
This feast was named Pentecost because commemorated on this day was an event in the Old Testament called the feast of Pentecost, and also because this feast necessarily comes 50 days after the Christian Pascha. Especially important is the concurrence of the time of the descent of the Holy Spirit with the time of the Old Testament feast of Pentecost. The descent of the Holy Spirit on the believers in Christ was the crowning of the redemption and salvation of man by God. During the time of Pentecost the disciples of the Lord have blossomed and have grown spiritually; then the fullness of the gifts of the Spirit of God descended on them, and they became the first fruits of the redemptive work of Christ. Together with these revelations, the Church of Christ began on earth .
The day of Pentecost was the day, when the Old Testament theocracy which began on Sinai and ruled the people through the written law, the law of slavery and of death, was replaced by the New Testament law, where the people are led by the Spirit of God, the spirit of adoption and freedom (Rom. 8). Thus, as the Pascha of Christ abolished the Old Testament Pascha, the New Testament Pentecost replaces the Old Testament one, from which life under the law began.
In the hymns of the church for the day of Pentecost the event, the descent of the Holy Spirit on the apostles, and the beneficial fruits of this great event are praised.
«Today», – sings the Holy Church, – wondrous things were done before the face of all peoples «in the city of David, when the Holy Spirit came down as fiery tongues», upon the disciples of Christ; now «The Spirit of salvation, purifying the hearts of the apostles»; now, «the apostles clothed with the power from on high by Christ: for the Comforter revives them»; now, the Holy Spirit «revealed the unlettered to be orators», the fishermen, «bridling the mouths of sophists in abundance with a word, and raising from the deep night unnumbered people»; «they know in three persons One unerring, unapproachable, timeless Essence; for light has shone, the grace of the Spirit «; «When the power of the divine Spirit came down, it divinely united in one harmony the voice divided of old (i.e. the language of the people) of those who had wickedly agreed to Praising the Zion event and showing its fruits, the Holy Church lifts up our minds and hearts even to the knowledge of God’s attributes and actions of the Heavenly Visitor, the Spirit of God.
In the words of St. Gregory the Theologian: «The Holy Spirit always was, and is, and will be; neither beginning nor coming to an end, but always ranked and numbered with the Father and the Son»; «He is the life and creator of life; He is the light and the bestower of light; He is the pouring out of goodness and source of goodness»; «through Whom the Father is known and the Son (John 16:14) is glorified, and by all is known»; «He is the Spirit of wisdom, understanding»; «He is God and deifier.» «He distributes the gifts » (1 Cor. 12:11), «crowns the prophets, apostles and martyrs «.
Glorifying the Holy Spirit, the solemn Worship of the actual day also includes within itself the thanksgiving glorification of our Lord Jesus Christ, «Who on this final great and saving day of Pentecost revealed to us the mystery of the Holy, Consubstantial, Coeternal, Undivided and Uncompounded Trinity», and «poured out the Comforter upon the disciples, as was promised», and «setting them as Evangelists of our true faith, revealing them as confessors and heralds of true theology».
«In your courts», exclaims the Holy Church, «I will sing your praise, as the Savior of the world, and bending the knee I will worship your invincible power, at evening and morning and midday, and at every moment I will bless you, O Lord.»
The Holy Church uplifts also the general doxology to the Most Holy Trinity and inspires us, that we, «bending the knee of souls and body», praise you «the Father without beginning, and the Son, likewise without beginning, and Co-eternal and All Holy Spirit», «the Trinity One in Essence», «Identical in power and Coeternal «.
«Come, you people,» the Church appeals to its children, «let us worship the Godhead in three persons, the Son in the Father, with the Holy Spirit; for the Father timelessly begot the Son, co-eternal and co-reigning, and the Holy Spirit was in the Father, glorified with the Son; one power, one essence, one Godhead.»
But that our glorifications do not remain fruitless, the Holy Church often appeals to the very Spirit Comforter with the prayer: «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. »
From the Bulgakov Handbook
 Pentecost for the Jews was one of the three great annual feasts (Exodus. 23:14, 16, 17; Deut. 16:16). By the day of Pentecost the Jews had finished the harvest, which began with the feast of Pascha, according to that the fiftieth day after the first day of Pascha was actually the feast of the ending of the harvest, in which under the law they should offer to God a thanksgiving sacrifice from fruits of the earth. (Exodus. 23:16; Num. 28:26). Over time this feast began to incorporate and commemorate the giving of the Sinai law received by the Hebrews within 50 days after their exodus from Egypt. For the Jews this feast was solemn and joyful (Deut. 16:11), and for this feast they flocked to Jerusalem in great numbers. Each of them considered it a sacred duty to visit the Holy City, in order to bring in gratitude to God the sacrifice from the gathered harvest, established by the law, (Lev. 23:17, 30), and it was considered obligatory not only for Palestinian Jews, but also for those outside of Palestine living
 The mighty wind was closest to the prophecy, and the appearance of fiery tongues was seen as the sign of the coming of the Holy Spirit. The mighty wind and vision of fiery tongues proceeded not for long, maybe for a moment; but the Holy Spirit has always poured himself out into the souls and hearts of the believer. Being most pure and bodiless, the Holy Spirit has selected a physical sign to more perceptively manifest His presence. «For», reasoned St. Gregory the Theologian, «as the Son of God was seen to be visible on earth, it also was necessary for the Holy Spirit to be seen to be visible. But «yes who will not think», teaches St. Leo the Great, «that what was visible with physical eyes was the most Divine essence of the Holy Spirit.» «That which actually belongs to His essence is hidden in His Divinity, because human sight, as it cannot see the Father and Son, also cannot see the Holy Spirit». «According to His nature the Holy Spirit is invisible, similar to the Father and Son;
 These fools, who dared to explain to one another what they did not at all understand, «sneering, said» that the apostles «drank sweet wine» (a favorite morning drink in antiquity)». Thus blasphemous levity always sneers at sacred inspiration. So they always also are cold to subjects of faith: if they are not able to understand something, then they make an effort to make fun of anyone who speaks of higher things. Carnal people do not know of other pleasures, except for the sensual; they judge from their own experience, and – blaspheme!
 «Brightly and triumphantly», says His Grace Theophanes, Bishop of Tambov, «the Holy Church celebrates the descent of the Holy Spirit on the Apostles.» And how can she not celebrate? Because the Holy Spirit actually created the Church of God on the foundation established in the Lord Jesus Christ: He finally reveals and explains to the Apostles the mysteries of the kingdom and the entire Christian teaching, by Him all languages are mastered and are given to the hearers of the faith, He bestows all powers «to those living in godliness, He is the source of all their rules and institutions for the development, strengthening and protection of the believers, He from here on keeps whole and undamaged the pledge of our salvation. Remembering this great work of God, the Holy Church can exult and praise the great in her.
 In this hymn it is pointed out that with the same descent of the Holy Spirit appeared the gifts of God, there never was punishment for the self-deluded pride of the people. There never was a time, when «all the earth would speak with one mouth and with one voice.» But the people, who were threatened with dispersion and slavery, thought, contrary to any definition of God’s Providence, by general consensus and with the ability to fulfill an insane enterprise, began to build a tower up to Heaven to get glory for them and so not be dispersed over all the earth. Then God sent down various languages to the unreasonable workers, and it so divided them that they were not able to finish the work, because of the differences among the parties. (Gen. 11). Now the division of languages appears as such a heavenly gift, which up to now divided and separated the nationalities, is through the preaching of the Gospel brought all together in one entirety, in one Church of Christ.