But the mercy of the LORD is from everlasting to everlasting upon them that fear him, and his righteousness unto children's children;

But the lovingkindness of Jehovah is from everlasting to everlasting upon them that fear him, And his righteousness unto children's children;

But the mercy of the Lord is from eternity and unto eternity upon them that fear him: And his justice unto children's children,

And the kindness of Jehovah Is from age even unto age on those fearing Him, And His righteousness to sons' sons,

But the mercy of the Lord is eternal for his worshippers, and their children's children will see his righteousness;

But the goodness of Jehovah, etc The Psalmist leaves nothing to men to rely upon but the mercy of God; for it would be egregious folly to seek a ground of confidence in themselves. After having shown the utter emptiness of men, he adds the seasonable consolation, that, although they have no intrinsic excellence, which does not vanish into smoke, yet God is an inexhaustible fountain of life, to supply their wants. This contrast is to be particularly observed; for whom does he thus divest of all excellence? The faithful who are regenerated by the Spirit of God, and who worship him with true devotion, these are the persons whom he leaves nothing on which their hope may rest but the mere goodness of God. As the Divine goodness is everlasting, the weakness and frailty of the faithful does not prevent them from boasting of eternal salvation to the close of life, and even in death itself. David does not confine their hope within the limits of time -- he views it as commensurate in duration with the grace on which it is founded. To goodness is subjoined righteousness, a word, as we have had occasion frequently to observe before, denoting the protection by which God defends and preserves his own people. He is then called righteous, not because he rewards every man according to his desert, but because he deals faithfully with his saints, in spreading the hand of his protection over them. The Prophet has properly placed this righteousness after goodness, as being the effect of goodness. He also asserts that it extends to the children and children's children, according to these words in Deuteronomy 7:9, "God keepeth mercy to a thousand generations." It is a singular proof of his love that he not only receives each of us individually into his favor, but also herein associates with us our offspring, as it were by hereditary right, that they may be partakers of the same adoption. How shall He cast us off, who, in receiving our children and children's children into his protection, shows to us in their persons how precious our salvation is in his sight? Farther, as nothing is more easy than for hypocrites to flatter themselves under a false pretext, that they are in favor with God, or for degenerate children groundlessly to apply to themselves the promises made to their fathers, it is again stated, by way of exception, in the 18th verse, that God is merciful only to those who, on their part, keep his covenant, which the unbelieving make of none effect by their wickedness. The keeping, or observing of the covenant, which is here put instead of the fear of God, mentioned in the preceding verse, is worthy of notice; for thus David intimates that none are the true worshippers of God but those who reverently obey his Word. Very far from this are the Papists, who, thinking themselves equal to the angels in holiness, nevertheless shake off the yoke of God, like wild beasts, by trampling under foot his Holy Word. David, therefore, rightly judges of men's godliness, by their submitting themselves to the Word of God, and following the rule which he has prescribed to them. As the covenant begins with a solemn article containing the promise of grace, faith and prayer are required, above all things, to the proper keeping of it. Nor is the additional clause superfluous -- who remember his statutes; for, although God is continually putting us in mind of them, yet we soon slide away to worldly cares -- are confused by a multiplicity of avocations, and are lulled asleep by many allurements. Thus forgetfulness extinguishes the light of truth, unless the faithful stir up themselves from time to time. David tells us that this remembrance of God's statutes has an invigorating effect when men employ themselves in doing them. Many are sufficiently forward to discourse upon them with their tongues whose feet are very slow, and whose hands are well nigh dead, in regard to active service.

But the mercy of the Lord - The favor of the Lord; or, his loving-kindness.
Is from everlasting to everlasting - Is from the eternity past to the eternity to come. It had its foundation in the eternal decrees of God; it has its security in his purpose that where it is conferred, it shall not be withdrawn. It had no beginning; it will have no end. There never was a period in the past when it was not the purpose of God to save his people; there never will be a period in the future when it will be said that his saving mercy has ceased. It would be difficult to think of a statement which would at the same time, in so few words, confirm at once the doctrine of the divine decrees, and the doctrine of the perseverance of the saints. If either of these doctrines is denied, then what is here stated by the psalmist is not true: if the doctrine of the divine decrees is denied, then his purpose of mercy had a beginning, and is not "from everlasting;" if the doctrine of the perseverance of the saints is denied, then his mercy has an end, and is not "to everlasting."
Upon them that fear him - In respect to those who are his true worshippers, or his true people.
And his righteousness - His righteous purpose; or, his purpose in regard to their "becoming" righteous.
Unto children's children - literally, "sons of sons." That is, his purposes embrace the children and children's children of the righteous; or, they are included in the covenant of mercy. See the notes at Acts 2:39. Compare Exodus 20:6.

The mercy of the Lord is from everlasting to everlasting - חסד chesed signifies more particularly the exuberant goodness of God. This is an attribute of his nature, and must be from everlasting to everlasting; and hence, his righteousness (צדקת tsidketh) - his merciful mode of justifying the ungodly, is extended from one generation to another.
Unto children's children - It is still in force, and the doctrine of reconciliation through Christ shall continue to be preached till the conclusion of time.

But the mercy of the LORD [is] from everlasting to everlasting upon them that fear him, and his (k) righteousness unto children's children;
(k) His just and faithful keeping of his promise.

But the mercy of the Lord is from everlasting to everlasting upon them that fear him,.... In opposition to the frailty of man, the stability and duration of the mercy of God is observed. This reaches from one eternity to another; it is from everlasting in the heart of God: it appeared in the choice of the vessels of mercy; in the covenant of grace, which is founded upon it, and filled with it; every blessing of which flows from it, and therefore are called the "sure mercies of David". And it appears in time in the regeneration of God's elect, which is according to his abundant mercy; in the forgiveness of their sins, which is according to the multitude of his tender mercies; and in their whole salvation, which is by that, and not by works of righteousness; and will endure for ever, for the mercy of our Lord Jesus Christ is unto eternal life. It reaches from the world past to the world to come, as the Targum; and it is so "upon them that fear" the Lord; not with a servile, but a filial fear; a fear of the Lord and his goodness; which only is consistent with the grace and mercy of God, and a sense of it: not that the fear of God is the cause of mercy or grace; but, on the contrary, grace and mercy are the cause of the fear of God; which is a blessing of the covenant of grace, and one of the first things which appear in conversion; but this properly describes the persons who openly and manifestly share in the grace or mercy of God, and to whom he manifests it yet more and more; nor have any reason to believe they are the objects of it, until the true fear of God is wrought in their hearts; and, besides, this character may be given to show that the mercy and grace of God are not limited to the Israelites only, but belong to such of all nations that fear the Lord.
And his righteousness unto children's children; not the essential righteousness of God, but rather his faithfulness in the performance of his promises, which he will not suffer to fail: the justifying righteousness of Christ is here meant; which is an everlasting one, and is unto and upon all them that believe, in all successive generations; which is meant by the phrase of "children's children", even the spiritual seed of Christ, the seed of the church, the seed of Israel; to all and each of which, in every age, the word of God comes, and his promises are fulfilled; and who are justified by and glory in Christ, their righteousness; and who are further described in the next verse, which shows that not the carnal seed of them that fear the Lord are meant.

For similar contrast compare Psalm 90:2-6; Psalm 102:27-28.