St Gregory of Nazianzus – Hold fast to the Trinity

I set before you the One Deity and Power,
Found in the Three-in-Unity,
Embracing the Three one by one, equal in essence and nature,
Neither increased nor decreased by ideas of greater or less;
In every way equal, in every way the same,
Just as the loveliness and hugeness of the heavens are one:
The infinite oneness of Three Infinite Ones,
Each of whom is God when seen individually in Himself.
As the Father is God, so is the Son,
And as the Son is God, so is the Holy Spirit;
And the Three are likewise One God when seen together.
Each is God because they are of the same essence,
And they are One God because of the single principle of Deity.
The very instant I conceive of the One,
I am enlightened by the brightness of the Three;
The very instant is differentiate them,
I am carried straight back to the One.
When I regard any One of the Three, I think of Him as the Whole;
My sight is filled to the brim,
And the greater part of what I am thinking of eludes me!
I cannot grasp the greatness of One of the Three
So as to reckon a greater greatness to the Others.
And when I see the Three together, I see only one torch,
And I cannot divide or share out the Undivided Light.

-Gregory the Theologian, Oration on Holy Baptism, ch. 41, translated by Nick Needham, Daily Readings: The Early Church Fathers, March 7