Gregory of Nyssa writes: "That the Egyptian tyrant was hardened must not be understood as though God deliberately implanted hardened resistance in his soul by His power. It happened because his free choice, by its inclination toward evil, did not accept the word whose aim was to soften his hardness" (in Oecumenius).
Basil the Great says: "God hardened Pharaoh by long-suffering and by the suspension of punishments, strengthening his evil character, so that when his malice had grown to its final measure, God's judgment upon him might appear righteous" (in Oecumenius).
Blessed Theophylact writes: "What does 'He hardens' mean? This appears absurd. Yet it is said of God that He hardened Pharaoh's filthy heart in the same way that the sun hardens mud. How so? By long-suffering, for He makes him hard by showing long-suffering toward him. Here there happened something like what occurs when someone has a wicked servant and treats him humanely. The more humanely he treats him, the worse he makes him, not because he himself teaches him vice, but because the servant uses his long-suffering to increase his own wickedness, since he despises his long-suffering."
Just as God has mercy on those who are worthy of mercy, and who, although they sin, repent or are foreseen as going to repent, so one must understand that He hardens those who are unworthy. These are those who, when they sin against God, not only do not repent, but become still more obstinate against Him.
Oecumenius writes: "God has mercy on the one worthy of mercy, but He leaves the hard-hearted and disobedient to remain hardened. For the present time is not the time of final judgment, but of voluntary struggle and free life. 'He hardens' stands for 'He permits him to remain hardened,' yielding to free choice."
Or, by contrast with the word "has mercy," "hardens" may be replaced by "does not have mercy," "rejects," "deprives of blessing and of the inheritance of the promise." From all the examples and reasonings presented, it is clear that God declares His promise to the worthy, and makes the worthy its heirs. The promise does not concern the unworthy, and therefore they do not become its heirs.
This is a direct proof that, although many Jews have now not entered the inheritance of the spiritual blessings promised to their fathers, the promise has not thereby failed. Such is the meaning of the promise: only the worthy can inherit it. If there are those who do not inherit it, it is plainly because they are unworthy.
The Apostle expresses this by referring everything to God: "Whom He wills, He has mercy on; whom He wills, He does not have mercy on." By this he teaches "that an account must not be demanded from God" (blessed Theophylact). He is always right when He acts according to His will, which is always righteous and good.
In the present case, they prove unworthy because they do not believe. If they had believed and were still alienated, then the promise would have failed. But since they are alienated because of unbelief, the promise stands and has not failed. No one compels them not to believe. They themselves do not believe. Therefore they themselves are guilty of being alienated from the blessings promised in the Deliverer. Let them believe, and they will enter into their inheritance.
But from the fact that they persist in unbelief, it does not follow that the promise has failed. Let them not lull themselves with the promise. Rather, let them quickly take into consideration the fearful example of Pharaoh, whose obstinacy brought him to the punishment of being drowned in the sea. Let them fear lest they themselves live to see something similar.