Thanks for the quotes, Schultz. Fr. John mentioned the Scripture passage which says that God alone has immortality (1 Tim. 6:15-16). And fwiw, here are the passages from the Church Fathers that Fr. John mentioned in his book related to the Orthodox position on created beings having immortality…
St. John of Damascus, Exact Exposition of the Orthodox Faith, 2, 3...
An angel, then, is an intelligent essence, in perpetual motion, with free-will, incorporeal, ministering to God, having obtained by grace an immortal nature: and the Creator alone knows the form and limitation of its essence. But all that we can understand is, that it is incorporeal and immaterial. For all that is compared with God Who alone is incomparable, we find to be dense and material. For in reality only the Deity is immaterial and incorporeal.
Tatian, Address to the Greeks, 13...
The soul is not in itself immortal, O Greeks, but mortal. Yet it is possible for it not to die.
St. Irenaeus, Against Heresies, 5, 13, 3...
For thus they will allege that this passage refers to the flesh strictly so called, and not to fleshly works, as I have pointed out, so representing the apostle as contradicting himself. For immediately following, in the same Epistle, he says conclusively, speaking thus in reference to the flesh: “For this corruptible must put on incorruption, and this mortal must put on immortality. So, when this mortal shall have put on immortality, then shall be brought to pass the saying which is written, Death is swallowed up in victory. O death, where is your sting? O death, where is your victory?” 1 Corinthians 15:53 Now these words shall be appropriately said at the time when this mortal and corruptible flesh, which is subject to death, which also is pressed down by a certain dominion of death, rising up into life, shall put on incorruption and immortality. For then, indeed, shall death be truly vanquished, when that flesh which is held down by it shall go forth from under its dominion.
And again, to the Philippians he says: “But our conversation is in heaven, from whence also we look for the Saviour, the Lord Jesus, who shall transfigure the body of our humiliation conformable to the body of His glory, even as He is able (ita ut possit) according to the working of His own power.” Philippians 3:29, etc. What, then, is this “body of humiliation” which the Lord shall transfigure, [so as to be] conformed to “the body of His glory?” Plainly it is this body composed of flesh, which is indeed humbled when it falls into the earth. Now its transformation [takes place thus], that while it is mortal and corruptible, it becomes immortal and incorruptible, not after its own proper substance, but after the mighty working of the Lord, who is able to invest the mortal with immortality, and the corruptible with incorruption. And therefore he says, “that mortality may be swallowed up of life. He who has perfected us for this very thing is God, who also has given unto us the earnest of the Spirit.” 2 Corinthians 5:4 He uses these words most manifestly in reference to the flesh; for the soul is not mortal, neither is the spirit. Now, what is mortal shall be swallowed up of life, when the flesh is dead no longer, but remains living and incorruptible, hymning the praises of God, who has perfected us for this very thing. In order, therefore, that we may be perfected for this, aptly does he say to the Corinthians, “Glorify God in your body.” 1 Corinthians 6:20 Now God is He who gives rise to immortality.
St. Irenaeus, Against Heresies, 3, 20, 1-2...
[This was done] that man, receiving an unhoped-for salvation from God, might rise from the dead, and glorify God, and repeat that word which was uttered in prophecy by Jonah: “I cried by reason of my affliction to the Lord my God, and He heard me out of the belly of hell;” Jonah 2:2 and that he might always continue glorifying God, and giving thanks without ceasing, for that salvation which he has derived from Him, “that no flesh should glory in the Lord's presence;” (1 Cor. 1:29) and that man should never adopt an opposite opinion with regard to God, supposing that the incorruptibility which belongs to him is his own naturally, and by thus not holding the truth, should boast with empty superciliousness, as if he were naturally like to God. For he (Satan) thus rendered him (man) more ungrateful towards his Creator, obscured the love which God had towards man, and blinded his mind not to perceive what is worthy of God, comparing himself with, and judging himself equal to, God.
This, therefore, was the [object of the] long-suffering of God, that man, passing through all things, and acquiring the knowledge of moral discipline, then attaining to the resurrection from the dead, and learning by experience what is the source of his deliverance, may always live in a state of gratitude to the Lord, having obtained from Him the gift of incorruptibility, that he might love Him the more; for “he to whom more is forgiven, loves more:” Luke 7:43 and that he may know himself, how mortal and weak he is; while he also understands respecting God, that He is immortal and powerful to such a degree as to confer immortality upon what is mortal, and eternity upon what is temporal; and may understand also the other attributes of God displayed towards himself, by means of which being instructed he may think of God in accordance with the divine greatness.
St. Justin Martyr, Dialogue With Trypho, 5…
Old Man: These philosophers know nothing, then, about these things; for they cannot tell what a soul is.
Justin: It does not appear so.
Old Man: Nor ought it to be called immortal; for if it is immortal, it is plainly unbegotten.
Justin: It is both unbegotten and immortal, according to some who are styled Platonists.
Old Man: Do you say that the world is also unbegotten?
Justin: Some say so. I do not, however, agree with them.
Old Man: You are right; for what reason has one for supposing that a body so solid, possessing resistance, composite, changeable, decaying, and renewed every day, has not arisen from some cause? But if the world is begotten, souls also are necessarily begotten; and perhaps at one time they were not in existence, for they were made on account of men and other living creatures, if you will say that they have been begotten wholly apart, and not along with their respective bodies.
Justin: This seems to be correct.
Old Man: They are not, then, immortal?
Justin: No; since the world has appeared to us to be begotten.
Old Man: But I do not say, indeed, that all souls die; for that were truly a piece of good fortune to the evil. What then? The souls of the pious remain in a better place, while those of the unjust and wicked are in a worse, waiting for the time of judgment. Thus some which have appeared worthy of God never die; but others are punished so long as God wills them to exist and to be punished.
Justin: Is what you say, then, of a like nature with that which Plato in Timæus hints about the world, when he says that it is indeed subject to decay, inasmuch as it has been created, but that it will neither be dissolved nor meet with the fate of death on account of the will of God? Does it seem to you the very same can be said of the soul, and generally of all things? For those things which exist after God, or shall at any time exist, these have the nature of decay, and are such as may be blotted out and cease to exist; for God alone is unbegotten and incorruptible, and therefore He is God, but all other things after Him are created and corruptible. For this reason souls both die and are punished: since, if they were unbegotten, they would neither sin, nor be filled with folly, nor be cowardly, and again ferocious; nor would they willingly transform into swine, and serpents, and dogs and it would not indeed be just to compel them, if they be unbegotten. For that which is unbegotten is similar to, equal to, and the same with that which is unbegotten; and neither in power nor in honour should the one be preferred to the other, and hence there are not many things which are unbegotten: for if there were some difference between them, you would not discover the cause of the difference, though you searched for it; but after letting the mind ever wander to infinity, you would at length, wearied out, take your stand on one Unbegotten, and say that this is the Cause of all. Did such escape the observation of Plato and Pythagoras, those wise men, who have been as a wall and fortress of philosophy to us?