§ 131. The Divine Services of the Feast of the Holy Trinity or Pentecost. The festival of Pentecost was inaugurated to commemorate the coming down of the Holy Spirit upon the Apostles in the form of fiery tongues. It is called Pentecost because the event happened fifty days after the resurrection of Christ, and it coincides with the Old Testament feast of Pentecost, which commemorated the giving of the Law on Sinai. The feast is also called Trinity Day because, with the descent of the Holy Spirit upon the Apostles, the providential activity of the All-Holy Trinity in the salvation of men was made fully manifest. God the Father sent down the Holy Spirit through the redeeming ministry of the Son of God, our Lord Jesus Christ. It is for this reason that the Holy Church invites the faithful to fall down and worship the Tri-Hypostatic Divinity in a special way, worshipping “the Son in the Father with the Holy Spirit.” Acelebration of the Holy Spirit Himself is appointed for the day after Holy Pentecost, on the Monday, which we therefore call “Spirit day.” The origins of the celebration of Trinity Day reach back to the age of the Apostles.

The hymns of the feast contain the following themes: a) they paint a picture of the outward circumstances of the Descent of the Holy Spirit upon the Apostles - the gathering of the Disciples, the noise from heaven, the fiery tongues, the preaching of the Apostles in various languages and so on; b) they depict the interior change that the Apostles experienced - their gaining wisdom, their being granted the gift of tongues, and the Divine characteristics of the Holy Spirit - the Heavenly King, the Comforter, the Spirit of truth, Light, the Source of goodness, the Spirit of wisdom, the Spirit of understanding, the Dispenser of gifts, - and His grace-filled activity - the illumination through prophecy, the establishment of the sacred ministry of the priesthood, the renewal of the mind, instruction in wisdom; c) a description of the hypostatic characteristics of the Holy Trinity and or Their unity in Essence; d) a description of how the descent of the Holy Spirit completed the plan of the Divine dispensation regarding the salvation of man.

The appointed Old Testament readings are as follows:-

The first (Numbers 11:16-17, 24-29) tells how the Lord commanded Moses to choose seventy men from the elders of Israel to govern the people and to bring them (the elders) to the Tabernacle, and how the Lord came down in a cloud and they began to prophesy. The second (Joel 2:23-32) foretells the pouring out of the Holy Spirit upon all the flesh of mankind. The third (Ezekiel 36;24-28) speaks of the renewal of the souls of the faithful by the grace of the Holy Spirit, and that they will have a new heart and will fulfil the commandments of God.

The Canon of the feast of Pentecost is a hymn in honour of the Holy Trinity and particularly of the Holy Spirit. In it, the descent of the Holy Spirit upon the Apostles is hymned and seen as a witness of the fulfilment of the promise of the Saviour. The age-old prophesies concerning the sending down of the Holy Spirit upon all flesh are commemorated here, and the being of the Holy Spirit, the Third Hypostasis of the Holy Trinity, is hymned as One equal to God the Father and to God the Son. In the canon there are also set forth the circumstances of the descent of the Holy Spirit upon the Apostles, as recorded by Saint Luke in the Acts of the Apostles (2:1-13), and it describes the importance and beneficial effect of this sacred event: from this moment, after the descent of the Holy Spirit, the Holy Trinity, as it were, enters into the New Covenant with the redeemed race of man. The descent of the Holy Spirit can thus be accepted by the faithful as the origin of innumerable benefactions of the Divine Comforter.