The texts and hymns of the Feast of Pentecost reveal to us the Trinity.   

In the Vespers of Pentecost, we find several hymns that are sung throughout the liturgical year; indeed they are essential and appear at important moments in the life of the Church.   The very beautiful prayer, “O Heavenly King,” for example, was composed for Vespers for Pentecost.    We recite this hymn several times a day: at awakening, before study, before each important undertaking, at evening prayer, before sleep.  The priest recites it before every service, and particularly before celebrating the Eucharistic liturgy:

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. 

This is the only prayer addressed directly and personally to the Holy Spirit.   We call on him and ask him to be in us, as a personal gift.   We call the Holy Spirit “Heavenly King” because he leads us into the Kingdom of Heaven.   We call him “Comforter” because he wipes away all tears and changes all sorrow into joy, so that the love of God may dominate in all men and women.

Invoking the Holy Spirit, we speak to him as a person, as to One of the three who are one God.  The person of the Holy Spirit is hard to seize.  It is concealed behind his gifts:   the gift of prophecy, the gift of speaking in tongues, but especially faith, hope, and love.  But in giving these gifts, the Spirit gives himself.   He is the person-gift par excellence.  In giving himself, he identifies with our most intimate self and introduces us into this communion, which is the Trinity.

We have seen the true light!

We have received the heavenly Spirit!

We have found the true faith!

Worshipping the undivided Trinity,

who has saved us.

This prayer, too, comes to us from the Vespers of Pentecost.   We express our thanks to the Holy Trinity, which reveals itself to us at Pentecost.   We repeat this hymn at every Eucharist after communion, for Pentecost continues; it is not just a past event, and its action continues forever.  We are in the season of Pentecost, receiving the gifts of the Spirit which have been poured out on all flesh since the earliest days of the Church.

With the following prayer, we receive a most beautiful instruction about the Holy Trinity.  This hymn shows us the bond of love which exists between the three Divine Persons, showing that we can contemplate the unity-trinity in God on the basis of each hypostasis [an individual, complete substance existing entirely in itself; an incommunicable substance: the term used by the Church to identify the Persons in the Holy Trinity and the union of the two natures in one Divine Person in Christ].

The following hymn is a long development of the Trisagion (Holy God, Holy Mighty, Holy Immortal).   We discover the communion which exists at the heart of the Trinity.  The flow of love, passing from one hypostasis to another, is like a dance which allows us at the same time to comprehend the unity and the trinity in God.   This perpetual movement leads to God’s opening up to the world.  Indeed, God turns toward his creation in order to allow it to enter into his love.    This flow of love among the hypostases and turned toward creation, is, in theological terms, called perichoresis [the penetration and indwelling of the three Divine Persons reciprocally in one another, thus bringing out the unity of the Divine Essence].

Hymn of Leo the Wise

Come, O people, let us worship the Divinity in Three Persons,

the Son in the Father with the Holy Spirit.

For the Father begets a Son,

beyond time and of the same royalty;

and the Holy Spirit is in the Father,

sharing the glory of the Son.

One Energy, one Essence, one Divinity,

we worship you and cry:

Holy God,

Who accomplished everything through the Son,

with the cooperation of the Holy Spirit;

Holy Mighty,

who has made us to know the Father,

and who sent the Holy Spirit into the world;

Holy Immortal,

who proceeds from the Father

and dwells in the Son;

Holy Trinity, glory to you!