Translated by Ch. Browne and J. Swallow.
III. When did these come into being? They are above all "When." But, if I am to speak with something more of boldness,—when the Father did. And when did the Father come into being. There never was a time when He was not. And the same thing is true of the Son and the Holy Ghost. Ask me again, and again I will answer you, When was the Son begotten? When the Father was not begotten. And when did the Holy Ghost proceed? When the Son was, not proceeding but, begotten—beyond the sphere of time, and above the grasp of reason; although we cannot set forth that which is above time, if we avoid as we desire any expression which conveys the idea of time. For such expressions as "when" and "before" and "after" and "from the beginning" are not timeless, however much we may force them; unless indeed we were to take the AEon, that interval which is coextensive with the eternal things, and is not divided or measured by any motion, or by the revolution of the sun, as time is measured.
How then are They not alike unoriginate, if They are coeternal? Because They are from Him, though not after Him. For that which is unoriginate is eternal, but that which is eternal is not necessarily unoriginate, so long as it may be referred to the Father as its origin. Therefore in respect of Cause They are not unoriginate; but it is evident that the Cause is not necessarily prior to its effects, for the sun is not prior to its light. And yet They are in some sense unoriginate, in respect of time, even though you would scare simple minds with your quibbles, for the Sources of Time are not subject to time.
IV. But how can this generation be passionless? In that it is incorporeal. For if corporeal generation involves passion, incorporeal generation excludes it. And I will ask of you in turn, How is He God if He is created? For that which is created is not God. I refrain from reminding you that here too is passion if we take the creation in a bodily sense, as time, desire, imagination, thought, hope, pain, risk, failure, success, all of which and more than all find a place in the creature, as is evident to every one. Nay, I marvel that you do not venture so far as to conceive of marriages and times of pregnancy, and dangers of miscarriage, as if the Father could not have begotten at all if He had not begotten thus; or again, that you did not count up the modes of generation of birds and beasts and fishes, and bring under some one of them the Divine and Ineffable Generation, or even eliminate the Son out of your new hypothesis. And you cannot even see this, that as His Generation according to the flesh differs from all others (for where among men do you know of a Virgin Mother?), so does He differ also in His spiritual Generation; or rather He, Whose Existence is not the same as ours, differs from us also in His Generation.
Reference address : https://www.elpenor.org/gregory-nazianzen/third-theological.asp?pg=2