Tadze
136 Thus, then, as if giving a reason why he had cause to weep much, and to mourn deeply for his sin, he says, “Righteous are You, O Lord, and true is Your judgment”. “You have commanded Your testimonies, righteousness, and Your truth exceedingly”. This righteousness of God and righteous judgment and truth, is to be feared by every sinner: for thereby all who are condemned are condemned of God; nor is there one who can righteously complain against the righteous God of his own damnation. Therefore the tears of the penitent are needful; since if his impenitent heart were condemned, he would be most justly condemned. He indeed calls the testimonies of God righteousness: for He proves himself righteous by giving righteous commandments. And this is truth also, that God may become known by such testimonies.
137. But what is it that follows: “My zeal has caused me to pine”; or, as other copies read, Your zeal? Others have also, “The zeal of Your house:” and, “has eaten me up,” instead of, “has caused me to pine.” This, as it seems to me, has been considered as an emendation to be introduced from another Psalm, where it is written, “The zeal of Your house has eaten me up:” a text quoted also, as we know, in the Gospel. The two words, however, “has caused me to pine,” and “has eaten me up,” are somewhat like. But the words, “my zeal,” which most of the copies read, occasion no dispute: for what wonder is it if every man pines away from his own zeal? The words read in other copies, “Your zeal,” signify a man zealous for God, not for himself: but there is no difficulty in using “my” in the same sense...The Psalmist's jealousy is therefore also to be understood in a good sense: for he adds the cause, and says, “Because mine enemies have forgotten Your words.”...
138. Then considering with himself with what a flame of love he burned for the commandments of God: “Fiery,” says he, “is Your word exceedingly, and Your servant has loved it”. Justly jealous was he of the impenitent heart in His enemies, who had forgotten God's word; for he endeavoured to bring them unto that which he himself most ardently loved.
139. “I am young, and of no reputation; yet do I not forget Your righteousnesses:” not as my enemies, who “have forgotten Your words”. The younger seems to grieve for those older than himself who had forgotten the righteousnesses of God, while he himself had not forgotten. For what means, “I am young, yet do I not forget”? save this, Those older than me have forgotten. For the Greek word is νεώτερος, the same as that used in the words above, “Wherewithal shall a young man cleanse his way?” This is a comparative, and is therefore well understood in its relation to some one older. Let us therefore here recognize the two nations, who were striving even in Rebecca's womb; when it was said to her, not from works, but of Him that calls, “The elder shall serve the younger.” But the younger says here that he is of no reputation: for this reason he has become greater: since “behold, they that were first are last, and they that were last first.”
140. It is no wonder that they have forgotten the words of God, who have chosen to set up their own righteousness, ignorant of the righteousness of God; but he, the younger, has not forgotten, for he has not wished to have a righteousness of his own, but that of God, of which he now also says, “Your righteousness is an everlasting righteousness, and Your law is the truth”. For how is not the law truth, through which came the knowledge of sin, and that which gives testimony of the righteousness of God? For thus the Apostle says: “The righteousness of God is manifested, being witnessed by the Law and the Prophets.”
141. On account of this law the younger suffered persecution from the elder, so that the younger says what follows: “Trouble and hardship have taken hold upon me: yet is my meditation in Your commandments”. Let them rage, let them persecute; as long as the commandments of God be not abandoned, and, after those commandments, let even those who rage be loved.
142. “Your testimonies are righteousness unto everlasting: O grant me understanding, and I shall live”. This younger one prays for understanding; which if he had not, he would not be “wiser than the aged;” but he prays for it in trouble and hardships, that he may thereby understand how contemptible is all that his persecuting enemies can take from him, by whom he says he has been despised. Therefore he has said, “and I shall live:” because if trouble and heaviness reached such a pitch, that his life should be terminated by the hands of his persecuting enemies, he will live for ever, who preferrs to temporal things, righteousness which remains for evermore. This righteousness in trouble and hardship are the Martyria Dei, that is, the testimonies of God, for which Martyrs have been crowned.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)