Your righteousness is an everlasting righteousness, And Your law is truth.
NASB95
Your righteousness is righteous forever, and your law is true.
ESV
Thy righteousness is an everlasting righteousness, and thy law is the truth.
KJV

The Psalmist in the midst of his trials could not forget the precepts, while he maintained so just a perception of their exalted character. His mind at this time seems to have been filled with the contemplation of the righteous government of God. He therefore repeats his adoration, not as applied to any particular instance, but as distinguishing the general character of His administration from everlasting.

But on whom is this government appointed to rest? Think of our Immanuel—the human brow encircled with Divine glory—the crucified hands wielding the scepter of the universe—Him, whom they mocked as the King of the Jews, seated on His own exalted throne, "King of Kings and Lord of lords!" "The government is upon His shoulder: and of the increase of His government and peace there shall be no end." How delightful to join Jehovah Himself in the ascription of praise, "Your throne, O God, is forever and ever; a scepter of righteousness is the scepter of Your kingdom!" How glorious also to praise that everlasting righteousness—the ground on which the administration of His church is framed—which Jesus "brought in," and "which is unto all them that believe;" which, when once clothed with it, is our infinite glory and reward!

"Every ordinance of man" is connected only with time. The Divine government has a constant reference to eternity, past and to come. "And I heard"—said the enraptured disciple, "the angel of the waters say; You are righteous, which are, and was, and shall be; because You have judged thus." Every instance, therefore, of His righteous administration, is that display of the Divine character which constrains the adoration of heaven. "One cried to another, and said, Holy, holy, holy, is the Lord of hosts: the whole earth is full of His glory." His law, "the manifestation of His righteousness"—is the truth. "Your word is true from the beginning! and everyone of Your righteous judgments endures forever."

This truth is the law of righteousness, which Jesus bound Himself to "fulfill"—to which He "came to bear witness," and for which He commended His people to His Father as the means of their sanctification; for what else is holiness, but the influence of truth, digested and practically embodied in the life and conduct? There may be fragments of truth elsewhere found—the scattered remnants of the fall. There may be systems imbued with large portions of truth deduced from this law. But here alone is it found perfect—unsullied. How carefully, therefore, should we test, by this standard, every doctrine—every revelation; receiving with implicit subjection all that is conformed to it; rejecting with uncompromising decision whatever will not abide the fiery trial. Most careful also should we be to preserve its unadulterated simplicity. Even the most seemingly trifling infusion of fundamental error is the grain of poison cast into the food, and making it "a savor of death unto death." Such was the error of the Galatian Church, "another gospel, yet not another"—not deserving the name—not putting ordinances in the stead of Christ (an error too gross to beguile a Christian profession), but what is far more subtle, and equally destructive, mixing them with Christ; thus impairing the integrity of the foundation, paralyzing the springs, poisoning the sources of life, yes, converting life itself into death. Let this church stand out as a beacon to our own—as a much-needed warning to each of her members.

But in a more general view, let us adore the Divine revelation, as bearing so full an impress of a "God that cannot lie"—of a "covenant ordered in all things" beyond human contrivance, "and sure" beyond the possibility of a change. How many dying testimonies have sealed the truth of the precious promises! Joshua, Simeon, and a "cloud of witnesses with which we are compassed about," have "set to their seals that God is true"—that "all the promises of God are in Christ Jesus yes and amen"—that "all are come to pass unto them, and not one thing has failed thereof." Equally manifest is the truth of His threatenings. Hell is truth seen too late. Those on the right hand and those on the left, at the great day of God, will combine their testimony to the declaration of the "Faithful and True Witness" "Heaven and earth shall pass away, but my words shall not pass away."

"Your righteousness is an everlasting righteousness." Having in a previous verse ascribed righteousness to God, he now goes on to declare that that righteousness is unchanging, and endures from age to age. This is the joy and glory of the saints, that what God is he always will be, and his mode of procedure towards the sons of men is immutable: having kept his promise, and dealt out justice among his people, he will do so world without end. Both the righteousness and the unrighteousness of men come to an end, but the righteousness of God is without end.

"And your law is the truth." As God is love, so his law is the truth, the very essence of truth: truth applied to ethics, truth in action, truth upon the judgment-seat. We hear great disputes about "What is truth." "The holy Scriptures are the only answer to that question. Note, that they are not only true, but the truth itself. We may not say of them that they contain the truth, but that they are the truth: "your law is the truth." There is nothing false about the law or preceptory part of Scripture. Those who are obedient thereto shall find that they are walking in a way consistent with fact; while those who act contrary thereto are walking in a vain show.

Because the word is true it has an everlasting righteousness about it To alter, diminish, or add, is to lie against God.