2 Timothy 2:13

What then meaneth, "Can do nothing of Himself"? That He can do nothing in opposition to the Father, nothing alien from, nothing strange to Him, which is especially the assertion of One declaring an Equality and entire agreement. But wherefore said He not, that "He doeth nothing contrary," instead of, "He cannot do"? It was that from this again He might show the invariableness and exactness of the Equality, for the expression imputes not weakness to Him, but even shows His great power; since in another place Paul saith of the Father, "That by two immutable things in which it was impossible for God to lie" (Heb. vi. 18): and again, "If we deny Him - He abideth faithful," for "He cannot deny Himself." (2 Tim. ii. 12, 2 Tim. ii. 13.) And in truth this expression, "impossible," is not declaratory of weakness, but power, power unspeakable. For what He saith is of this kind, that "that Essence admitteth not such things as these." For just as when we also say, "it is impossible for God to do wrong," we do not impute to Him any weakness, but confess in Him an unutterable power; so when He also saith, "I can of Mine own Self do nothing," His meaning is, that "it is impossible, nature admits not, that I should do anything contrary to the Father."

And to show this, he has added, "If we believe not, He abideth faithful: He cannot deny Himself": that is, if we believe not that He rose again, He is not injured by it. He is faithful and unshaken, whether we say so or not. If then He is not at all injured by our denying Him, it is for nothing else than for our benefit that He desires our confession. For He abideth the same, whether we deny Him or not. He cannot deny Himself, that is, His own Being. We may say that He is not; though such is not the fact. It is not in His nature, it is not possible for Him not to be, that is, to go into nonentity. His subsistence always abides, always is. Let us not therefore be so affected, as if we could gratify or could injure Him. But lest any one should think that Timothy needed this advice...