”But the mercy of the LORD is from everlasting to everlasting upon them that fear him, and his righteousness unto children’s children; To such as keep his covenant, and to those that remember his commandments to do them”. Psalm 103:17, 18.
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, 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 worshipers of God but those who reverently obey his Word. John Calvin