15 Here therefore what says he? “For your servants take pleasure in her stones”. In whose stones? In the stones of Sion? But there are those there that are not stones. Not stones of what? What then follows? “and pity the dust thereof.” I understand by the stones of Sion all the Prophets: there was the voice of preaching sent before, thence the ministry of the Gospel assumed, through their preaching Christ became known. Therefore your servants have taken pleasure in the stones of Sion. But those faithless apostates from God, who offended their Creator by their evil deeds, have returned to the earth, whence they were taken. They have become dust, they have become ungodly. But wait, Lord; bear with us, Lord; be long-suffering, O Lord: let not the wind rush in, and sweep away this dust from the face of the earth. Let your servants come, let them come, let them acknowledge in the stones your voice, let them pity the dust of Sion, let them be formed in your image: let the dust say, lest it perish, “Remember that we are but dust.” This of Sion: was not that which crucified the Lord, dust? What is worse, it was dust from the ruined walls; altogether dust it was, but nevertheless it was not in vain said of this dust, “Father, forgive them.” From this very dust there came a wall of so many thousands who believed, and who laid the price of their possessions at the Apostles' feet. From that dust then there arose a human nature formed and beautiful. Who among the heathen acted thus? How few are there whom we admire for having done thus, compared with the many thousands of these converts? At first suddenly three, afterwards five thousand; all living in unity, all laying the price of their possessions, when they had sold them, at the Apostles' feet, that it might be distributed to each, as each had need, who had one soul and one heart toward God. Who made this even of that very dust, but He who created Adam himself out of dust? This then is concerning Sion, but not in Sion only.
16. “The heathen shall fear Your Name, O Lord; and all the kings of the earth Your Majesty”. Now that You have pitied Sion, now that Your servants have taken pleasure in her stones, by acknowledging the foundation of the Apostles and Prophets; now that they have pitied her dust; so that man is formed, or rather re-formed, in life out of dust; hence preaching has increased among the heathen: let the heathen fear Your Name, let another wall approach also from the heathen, let the Corner Stone be recognised, let the two who come from different regions, but who no longer differ in belief, meet in close union.
17. “For the Lord shall build up Sion”. This work is going on now. O you living stones, run to the work of building, not to ruin. Sion is in building, beware of the ruined walls: the tower is building, the ark is in building; remember the deluge. This work is in progress now; but when Sion is built, what will happen? “And He will appear in His glory.” That He might build up Sion, that He might be a foundation in Sion, He was seen by Sion, but not in His glory: “we have seen Him, and He had no form nor comeliness.” But truly when He shall have come with His angels to judge, shall they not look then upon Him whom they have pierced? and they shall be put to confusion when too late, who refused confusion in early and healthful repentance.
18. “He has turned Him unto the prayer of the poor destitute, and despised not their desire”. This is going on now in the building of Sion: the builders of Sion pray, they groan: He is the one poor, because the poor are many; because the thousands among so many nations are one in Him, because He is the unity of the peace of the Church, He is one, He is many: one, through love: many, on account of His extension. Therefore we now pray, we now run: now, if any man has used to be otherwise, and lived differently, let him eat ashes as it were bread, and mingle his drink with weeping. Now is the time, when Sion is in building: now the stones are entering into the structure: when the building is finished, and the house dedicated, why do you run, to ask when too late, to beg in vain, to knock to no purpose, doomed to abide without with the five foolish virgins? Therefore now run.
19. “Let these things be written for those that come after”. When these words were written, they profited not so much those among whom they were written for they were written to prophesy the New Testament, among men who lived according to the Old Testament. But God had both given that Old Testament, and had settled in that land of promise His own people. But since “Your remembrance is from generation to generation,” belongs not to the ungodly, but to the righteous; “in our generation” belongs to the Old Testament; while “in the other generation” belongs to the New Testament; and since the New Testament announces this that was prophesied, “Let these things be written for those that come after: and the people which shall be created, shall praise the Lord.” Not the people which is created, but “the people which shall be created.” What is clearer, my brethren? Here is prophesied that creation of which the Apostle says: “Therefore if any man be in Christ, he is a new creature; old things are passed away; behold, all things have become new.” “For he has looked down from His lofty sanctuary.” He has looked down from on high, that He might come unto the humble: from on high He has become humble, that He might exalt the humble....
20. “Out of the heaven did the Lord look down upon the earth”: “that He might hear the mournings of such as are in fetters, and deliver the children of such as are put to death”. We have found it said in another Psalm, “O let the sorrowful sighs of the fettered come before You;” and in a passage where the voice of the martyrs was meant. Whence are the martyrs in fetters?...But God had bound them with these fetters, hard indeed and painful for a season, but endurable on account of His promises, unto whom it is said, “On account of the words of Your lips, I have kept hard ways.” We must indeed groan in these fetters in order to gain the mercy of God. These fetters must not be shunned, in order to gain a destructive freedom and the temporal and brief pleasure of this life, to be followed by perpetual bitterness. Accordingly Scripture, that we may not refuse the fetters of wisdom, thus addresses us: “...Then shall her fetters be a strong defence for you, and her chains a robe of glory.” Let the fettered therefore cry out, as long as they are in the chains of the discipline of God, in which the martyrs have been tried: the fetters shall be loosed, and they shall fly away, and these very fetters shall afterwards be turned into an ornament. This has happened with the martyrs. For what have the persecutors effected by killing them, except that their fetters were thereby loosed, and turned into crowns?...The remission of sins, is the loosing. For what would it have profited Lazarus, that he came forth from the tomb, unless it were said to him, “loose him, and let him go”? Himself indeed with His voice aroused him from the tomb, Himself restored his life by crying unto him, Himself overcame the mass of earth that was heaped upon the tomb, and he came forth bound hand and foot: not therefore with his own feet, but by the power of Him who drew him forth. This takes place in the heart of the penitent: when you hear a man is sorry for his sins, he has already come again to life; when you hear him by confessing lay bare his conscience, he is already drawn forth from the tomb, but he is not as yet loosed. When is he loosed, and by whom is he loosed? “Whatsoever you shall loose on earth,” He says, “shall be loosed in Heaven.” Forgiveness of sins may justly be granted by the Church: but the dead man himself cannot be aroused except by the Lord crying within him; for God does this within him. We speak to your ears: how do we know what may be going on in your hearts? But what is going on within, is not our doing, but His.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)