15 But now in that which follows, “Let there come in before Your sight,” or, as some copies have it, “In Your sight, the groans of the fettered:” not easily does any one discover that the Saints were thrown into fetters by persecutors; and if this does happen amid so great and manifold a variety of punishments, so rarely it does happen, that it must not be believed that the prophet had chosen to allude to this especially in this verse. But, in fact, the fetters are the infirmity and the corruptibleness of the body, which do weigh down the soul. For by means of the frailty thereof, as a kind of material for certain pains and troubles, the persecutor might constrain her unto ungodliness. From these fetters the Apostle was longing to be unbound, and to be with Christ; but to abide in the flesh was necessary for their sakes unto whom he was ministering the Gospel. Until then this corruptible put on incorruption, and this mortal put on immortality, like as it were with fetters, the weak flesh does let the willing spirit. These fetters then not any do feel, but they that in themselves do groan being burthened, desiring to be clothed upon with the tabernacle which is from Heaven; because both death is a terror, and mortal life is sorrow. In behalf of these men groaning the Prophet does redouble his groaning, that their groaning may “come in in the sight of the Lord.” They also may be understood to be fettered, who are enchained with the precepts of wisdom, the which being patiently supported are turned into ornaments: whence it has been written, “Put your feet into her fetters.” “According to the greatness,” he says, “of Your arm, receive unto adoption the sons of them that are put to death:” or, as is read in some copies, “Possess sons by the death of the punished.” Wherein the Scripture seems to me to have sufficiently shown, what has been the groan of the fettered, who for the name of Christ endured most grievous persecutions, which in this Psalm are most clearly prophesied. For being beset with various sufferings, they used to pray for the Church, that their blood might not be without fruit to posterity; in order that the Lord's harvest might more abundantly flourish by the very means whereby enemies thought that she would perish. For “sons of them that were put to death” he has called them who were not only not terrified by the sufferings of those that went before, but in Him for whose name they knew them to have suffered, being inflamed with their glory which did inspire them to the like, in most ample hosts they believed. Therefore he has said, “According to the greatness of Your arm.” For so great a wonder followed in the case of Christian peoples, as they, who thought they would prevail anything by persecuting her, no wise believed would follow.
16. “Render,” he says, “to our neighbours seven times so much into their bosoms”. Not any evil things he is wishing, but things just he is foretelling and prophesying as to come. But in the number seven, that is, in sevenfold retribution, he would have the completeness of the punishment to be perceived, for with this number fullness is wont to be signified. Whence also there is this saying for the good, “He shall receive in this world seven times as much:” which has been put for all. “As if having nothing, and possessing all things.” Of neighbours he is speaking, because among them dwells the Church even unto the day of severing: for not now is made the corporal separation. “Into their bosoms,” he says, as being now in secret, so that the vengeance which is now being executed in secret in this life, hereafter may be known among the nations before our eyes. For when a man is given over to a reprobate mind, in his inward bosom he is receiving what he deserves of future punishments. “Their reproach wherewith they have reproached You, O Lord.” This do You render to them sevenfold into their bosoms, that is, in return for this reproach, most fully do You rebuke them in their secret places. For in this they have reproached Your Name, thinking to efface You from the earth in Your servants.
17. “But we Your people”, must be taken generally of all the race of godly and true Christians. “We,” then, whom they thought they had power to destroy, “Your people, and the sheep of your flock:” in order that he that glories may glory in the Lord, “will confess to You for an age.” But some copies have it, “will confess to You for everlasting.” Out of a Greek ambiguity this diversity has arisen. For that which the Greek has, εἰς τὸν αἰῶνα, may be interpreted both by “for everlasting,” and “for an age;” but according to the context we must understand which is the better interpretation. The sense then of this passage seems to me to show, that we ought to say “for an age,” that is, even unto the end of time. But the following verse after the manner of the Scriptures, and especially of the Psalms, is a repetition of the former with the order changed, putting that before which in the former case was after, and that after which in the former case was before. For whereas in the former case there had been said, “we will confess to You,” instead of the same herein has been said, “We will proclaim Your praise.” And so whereas in the former case there had been said, “for an age,” instead of the same herein has been said, “for generation and generation.” For this repetition of generation does signify perpetuity: or, as some understand it, it is because there are two generations, an old and a new....But in many places of holy Scriptures we have already made known to you that confession is also put for praise: as in this passage it is, “These words you shall say in confession, 'That the works of the Lord are very good.'” And especially that which the Saviour Himself says, who had not any sin at all, which by repentance to confess: “I confess to You, Father, Lord of heaven and earth, that You have hid these things from the wise and prudent, and hast revealed them to babes.” I have said this, in order that it may be more clearly perceived how in the expression, “We will proclaim Your praise,” the same has been repeated as had been said higher up, “We will confess to You.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)