28 But as far as regards the present passage of this Psalm, if we dare not ascribe those things which were marvellously formed out of creatures, to evil angels; we have a thing which without doubt we can ascribe to them; the dyings of the beasts, the dyings of the first-born, and this especially whence all these things proceeded, namely, the hardening of heart, so that they would not let go the people of God. For when God is said to make this most iniquitous and malignant obstinacy, He makes it not by suggesting and inspiring, but by forsaking, so that they work in the sons of unbelief that which God does duly and justly permit....Moreover, those evil manners which we said were signified by these corporal plagues, on account of that which was said before, “I will open in parables my mouth,” are most appropriately believed by means of evil angels to have been wrought in those that are made subject to them by Divine justice.
For neither when that comes to pass of which the apostle speaks, “God gave them over into the lusts of their heart, that they should do things which are not convenient,” can it be but that those evil angels dwell and rejoice therein, as in the matter of their own work: unto whom most justly is human haughtiness made subject, in all save those whom grace does deliver. “And for these things who is sufficient?” Whence when he had said, “He sent unto them the anger of His indignation, indignation and anger and tribulation, an infliction through evil angels;” for this which he has added, “a way He has made for the path of His anger”, whose eye, I pray, is sufficient to penetrate, so that it may understand and take in the sense lying hidden in so great a profundity?
For the path of the anger of God was that whereby He punished the ungodliness of the Egyptians with hidden justice: but for that same path He made a way, so that drawing them forth as it were from secret places by means of evil angels unto manifest offenses, He most evidently inflicted punishment upon those that were most evidently ungodly. From this power of evil angels nothing does deliver man but the grace of God, whereof the Apostle speaks, “Who has delivered us from the power of darkness, and has translated us into the kingdom of the Son of His love:” of which things that people did bear the figure, when they were delivered from the power of the Egyptians, and translated into the kingdom of the land of promise flowing with milk and honey, which does signify the sweetness of grace.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)