Dionysius the Areopagite: the source of the Divinity is the Father, and the Son and the Spirit are from the God-seeded Divinity and the God-planted branch, as the everlasting flowers are from the one Father. But it is impossible to say or see how this happens (In the manuscript of the Solovetsky Library No 331: "ni znaya.")

Epiphanius of Cyprus: We say "God the Father", "God the Son", "God the Holy Spirit", and not "Gods", for in the three names there is one Godhead. The Only-begotten Son proceeds from the Father, but the Holy Spirit, the Spirit of God, is ever with the Father and with the Son, for He proceeds from God the Father, and receives the Son's things, manifesting them in the world, and searches the depths of God, because the Son ascended to the Father, and the Father sent the Spirit in the Name of the Son, and the Holy Spirit, continuing the works of the Son, strengthened them and preached them clearly in the world.

St. Gregory the Wonderworker: There is one God, the Father of the living Word, one Lord God of God, one of one, one of one, one Holy Spirit, proceeding from God and manifested to mankind by the Son.

Damasus, Pope of Rome: Cursed be he who does not confess that the Holy Spirit truly proceeds from the Father, just as the Son proceeds from the Divine Being, and from God, God the Word.

Falassius Africanus: We all know that the Father is the one principle, the parent and source of the Son and the Spirit, co-existent, co-immeasurable and indefinable.

St. Cyril of Alexandria: In no way do we want anyone to damage the established faith, that is: "I believe in One God," the confession compiled by the Holy Fathers; for it was not they who said this, but the Spirit of God the Father, Who proceeds from Him and is not alienated from the Son, which is what the confession essentially says.

Caesarius, brother of Gregory the Theologian: the first true Light is the Father, and the Son is also Light, as He Himself said: "I am the light of the world" (John 8:12). The Spirit of God is also light, having the source of the Father, from Whom it proceeds.

Germanus, Patriarch of Constantinople: He who says that the Holy Spirit proceeds also from the Son, and says that the Son is the beginning of the existence of the Holy Spirit, like the Father, is worthy of condemnation and goes into perdition, because he belittles the Holy Spirit and destroys His honor.

Someone may say to this: The Son proceeds from the Father, but the Son is not less than the Father because He proceeds from the Father, so the Holy Spirit is not less than the Son because He proceeds from the Son.

But listen, you who object! For the Son has one Father as his cause and source, and the Holy Spirit, as you say, has two causes and two sources, that is, the Father and the Son, and from two, as you say, proceed one; but of the Son you do not say that He is born alone, or proceeds from two, but from one Father. And if you were to say that the Son also has two sources and two causes, the Father and the Holy Spirit, and the Holy Spirit also has two sources and two causes, the Father and the Son, then you would say that the Holy Spirit is equal to the Son. Now you speak of equality in words, but in deed you belittle it, supposing that the Holy Spirit has two sources and two causes, and the Son has one cause and source. Although the Son is equal in all things to the Father, you cannot say that the Son is the cause and source of the Father. But if you say this, know this: you have confused the Divine order, annoyed God, and perverted the Holy Scriptures. In the same way, if you say that the Holy Spirit proceeds from the Son, you have vexed God, you have confused the essence and order of the Divine Trinity, for the holy Church of God teaches that the Father has a Son and has the Holy Spirit, and we do not say that these are three gods, but that all three are one God, and they are equal both in essence and in divinity, and power. And although They are equal in all things, the Father is the source and cause of the Son and the Holy Spirit, and not the Son of the Father, nor the Spirit of the Holy Son, nor the Son of the Holy Spirit. Just as the Holy Spirit is neither the source nor the cause of the Son, so the Son is neither the source nor the cause of the Holy Spirit. But we say and believe that the Father is the cause of both, ineffable and incomprehensible to angels and to men, as the great Dionysius says: God is essentially incomprehensible, but His creation enables us to know and glorify Him, because through the visible we receive certain testimonies about God.

As the circle of the sun and the ray and the light are inseparable, so are the Father, the Son, and the Holy Spirit: the Father is the cause of the two, but not older, just as the sun is not older than the ray and the light. And if you say that the circle of the sun comes first, and the ray and the light later, you will say it wrong. And if you say that light and ray are before the solar circle, you will also say it wrong. You see that although all are one, the solar circle is the source and cause of both light and rays, just as the Father is the source and cause of the Son and the Holy Spirit. And if anyone says that the cause of the solar circle is a ray and light, he will say it wrongly, and everyone will answer him: you are possessed, and you do not understand simple things.

In the same way, he who says that the cause and source of the Father is the Son and the Holy Spirit will say it wrong, just as he is wrong who says that the cause and source of the Holy Spirit is not only the Father, but also the Son. Although among the Persons of the Holy Trinity there is not One Who was in the beginning and One Who was later, the source and cause of the Son and the Holy Spirit is the Father, and the Son Himself bears witness to Himself, saying: "My Father is greater than I" (John 14:28). This is said in a human way, but even more so as a judgment about the cause and source: for the Son was born of the Father, and not the Father of the Son. And if anyone says that the Holy Spirit proceeds from the Son, he asserts that just as the Father is the cause and source of the Son and the Holy Spirit, so the Son is the cause and source of the Holy Spirit. But if the Son, like the Father, were the source and cause of the Holy Spirit, then just as the Son said of the Father, "He is greater than I," so the Holy Spirit would say, "The Son is greater than Me, because He is My cause, and I proceed from Him." But this is not said anywhere! Although in the Holy Trinity there is no One Who was before and One Who was afterwards, and the Father, the Son, and the Holy Spirit are inseparably present, yet the Father is the one cause and source of the Son and the Holy Spirit, and the Son is not the source of the Holy Spirit. But if anyone says that the Son is also the source and cause of the Holy Spirit, for He proceeds also from the Son, he annoys God and produces the most evil confusion, all the more so since, according to Gregory the Theologian, in this case, God is also vexed and confused, and the creation is burdened with the dishonor of God.

And who would dare to speak of the Divine essence with an abominable tongue and filthy flesh, and not to learn from the Holy Scriptures, the writings of the prophets and apostles, from our holy and venerable and God-bearing fathers, thus gathering burning coals on his head? Therefore, we have chosen the testimonies from the holy books, and not our own, and have written them down in order, since they lead us to the right faith and do not allow us to get lost or perish. For, wearing the Apostolic Orthodoxy, the teachings of the Holy Councils and the teachings of our holy great-eminent fathers, as royal attire, we will become heirs of the Heavenly Kingdom – by the grace of the true, life-giving, omnipotent and omnipotent Holy Spirit, Who proceeds from the Father, and not from the Son, Who is due to worship and glorification together with the Father and the Son, and Who spoke through the prophets. The believer is "truly an Israelite, in whom there is no guile" (John 1:47), and such a person has truly come to know what God is and how it is proper to reason about God!

In addition, one must know how to worship the Lord God now.