7 But to prove that by His Grace He builds to Himself this place, not for the sake of the merits preceding of those persons out of whom He builds it, see what follows: “Who leads forth men fettered, in strength.” For He looses the heavy bonds of sins, wherewith they were fettered so that they could not walk in the way of the commandments: but He leads them forth “in strength,” which before His Grace they had not. “Likewise men provoking that dwell in the tombs:” that is, every way dead, taken up with dead works. For these men provoke Him to anger by withstanding justice: for those fettered men perchance would walk, and are not able, and are praying of God that they may be able, and are saying to Him, “From my necessities lead me forth.” By whom being heard, they give thanks, saying, “You have broken asunder my bonds.” But these provoking men that dwell in the tombs, are of that kind, which in another passage the Scripture points out, saying, “From a dead man, as from one that is not, confession perishes.” Whence there is this saying, “When a sinner shall have come into the depth of evil things, he despises.” For it is one thing to long for, another thing to fight against righteousness: one thing from evil to desire to be delivered, another thing one's evil doings to defend rather than to confess: both kinds nevertheless the Grace of Christ leads forth in strength. With what strength, but that wherewith against sin even unto blood they are to strive? For out of each kind are made meet persons, whereof to construct His holy place; those being loosened, these being raised to life. For even of the woman, whom Satan had bound for eighteen years, by His command He loosed the bonds; and Lazarus' death by His voice He overcame. He that has done these things in bodies, is able to do more marvellous things in characters, and to make men of one mood to dwell in a house: “leading forth men fettered in strength, likewise men provoking that dwell in the tombs.”
8. “O God, when You went forth before Your people”. His going forth is perceived, when He appears in His works. But He appears not to all men, but to them that know how to spy out His works. For I do not now speak of those works which are conspicuous to all men, Heaven and earth and sea and all things that in them are; but the works whereby He leads forth men fettered in strength, likewise men provoking that dwell in the tombs, and makes them of one manner to dwell in a house. Thus He goes forth before His people, that is, before those that do perceive this His Grace. Lastly, there follows, “When You went by in the desert, the earth was moved”. A desert were the nations, which knew not God: a desert they were, where by God Himself no law had been given, where no Prophet had dwelled, and foretold the Lord to come. “When,” then, “You went by in the desert,” when You were preached in the nations; “the earth was moved,” to the faith earthly men were stirred up. But whence was it moved? “For the heavens dropped from the face of God.” Perchance here some one calls to mind that time, when in the desert God was going over before His people, before the sons of Israel, by day in the pillar of cloud, by night in the brightness of fire; and determines that thus it is that “the heavens dropped from the face of God,” for manna He rained upon His people: that the same thing also is that which follows, “Mount Sina from the face of the God of Israel,” “with voluntary rain severing God to Your inheritance”, namely, the God that on Mount Sina spoke to Moses, when He gave the Law, so that the manna is the voluntary rain, which God severed for His inheritance, that is, for His people; because them alone He so fed, not the other nations also: so that what next he says, “and it was weakened,” is understood of the inheritance being itself weakened; for they murmuring, fastidiously loathed the manna, longing for victuals of flesh, and those things on which they had been accustomed to live in Egypt.... Lastly, all those men in the desert were stricken down, nor were any of them except two found worthy to go into the land of promise. Although even if in the sons of them that inheritance be said to have been perfected, we ought more readily to hold to a spiritual sense. For all those things in a figure did happen to them; until the day should break, and the shadows should be removed.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)