27 Thus then we see “the snow, the mist, the crystal:” it is good that He blow and thaw them. For if He blow not, if He Himself thaw not the hardness of this ice, “in the face of His cold who shall stand?” He abandons a sinner, behold, He calls him not; behold, He opens not his perception; behold, He pours not in grace; let the man thaw himself, if he can, from the ice of folly. He cannot. Wherefore can he not? “In the face of His cold who shall stand?” Behold him then growing harder, and saying, “O wretched man that I am! Who shall deliver me from the body of this death?” Behold, I am growing cold, behold, I am growing hard, what heat shall thaw me that I may run? “Who shall deliver me from the body of this death?....In the face of His cold who shall stand?” And who shall free himself, if God abandon him? Who is it that frees? “The grace of God, through Jesus Christ our Lord.” Are we then to despair? God forbid. For it goes on, “He shall send out His Word, and melt them”. Let not then the snow despair, nor the mist, nor the crystal. For of the snow, as of wool, a garment is being made. That mist finds safety in repentance: for, “whom He predestinated, them He also called.” But even though they be the very hardest among the predestinated, though they have been for a long time hardening, and have become crystal, they will not be hard to the mercy of God. “He shall send out His Word, and melt them.” What is “melt”? Understand not “melt” in an ill sense: it means, He shall liquefy, He shall thaw them. For they are hard through pride. Rightly is pride called also dulness: for whatever is dull, is also cold....Despair not even of the crystal. Hear a saying of the crystal. “Who before was a blasphemer, and a persecutor, and injurious.” But wherefore does God melt the crystal? That the snow despair not of itself. For he says, “For this cause I obtained mercy, that in me first Jesus Christ might show forth all long-suffering, for a pattern to them that hereafter should believe in Him unto eternal life.” God then calls unto the Gentiles, “Be melted, O crystal; come, you snows.” “His Spirit shall blow, and the waters shall flow.” Lo, the “crystal” and the “snows” are melted, they turn into water, “let them that thirst, come and drink.” Saul, hard as crystal, persecuted Stephen unto death; Paul, now in the living water, calls the Gentiles to the Fount....
28. “Announcing His Word unto Jacob, His Righteousnesses and Judgments unto Israel”. What “Righteousnesses,” what “Judgments”? Because whatever mankind had suffered here before, when it was “snow” and “mist” and “crystal,” it suffered for the deserts of its pride and uplifting against God. Let us go back to the origin of our fall, and see that most truly is it sung in the Psalm, “Before I was troubled I went wrong.” But he who says, “Before I was troubled I went wrong,” says also, “It is good for me that You have humbled me, that I may learn Your Righteousnesses.” These righteousnesses Jacob learned from God, who made him to wrestle with an Angel; under the guise of which Angel, God Himself wrestled with him. He held Him, he exerted violence to hold Him, he prevailed to hold Him: He caused Himself to be held, in mercy, not in weakness. Jacob therefore wrestled, and prevailed: he held Him and when he seemed to have conquered Him asked to be blessed of Him. How did he understand with Whom he had wrestled, Whom he had held? Wherefore did he wrestle violently, and hold Him? Because “the kingdom of heaven suffers violence, and the violent take it by force.” Wherefore then did he wrestle? Because it is with toil. Wherefore do we with difficulty hold, what we so easily lose? Lest, easily getting back what we have lost, we learn to lose that which we hold. Let man have toil to hold: he will hold firmly, what he has only held after toil. These His judgments therefore God manifested to Jacob and Israel....
29. “He has not done so to the whole race”. Let none deceive you: it is not announced to any nation, this judgment of God; namely, how the righteous and the unrighteous suffer, how all suffer for their deserts, how the righteous themselves are freed by the grace of God, not in their own merits. This is not announced to the whole race, but only to Jacob, only to Israel. What then do we, if He has not announced it to the whole race, but only to Jacob, only to Israel? Where will we be? In Jacob. “He has not manifested His judgments to them.” To whom? To all nations. How then are the “snows” called, when the crystal is melted? How are the nations called, now Paul is justified? How, save to be in Jacob? The wild olive is cut off from its stock, to be grafted into the olive: now they belong to the olive, no longer ought they to be called nations, but one nation in Christ, the nation of Jacob, the nation of Israel...What is Israel? “Seeing God.” Where shall he see God? In peace. What peace? The peace of Jerusalem; for, says he, “He has set peace for your borders.” There shall we praise: there shall we all be one, in One, unto One: for then, though many, we shall not be scattered.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)