17. O God! thou hast taught me from my youth; and hitherto will I announce thy wondrous works.18. And still, O God! when I am old and grey-headed, forsake me not, until I declare thy strength to the generation, and thy power to all who are to come.19. And thy righteousness, O God! Is very high: for thou hast done great things: O God! who is like thee?
17. O God! thou hast taught me from my youth. The Psalmist again declares the great obligations under which he lay to God for his goodness, not only with the view of encouraging himself to gratitude, but also of exciting himself to continue cherishing hope for the time to come: which will appear from the following verse. Besides, since God teaches us both by words and deeds, it is certain that the second species of teaching is here referred to, the idea conveyed being, that David had learned by continual experience, even from his infancy, that nothing is better than to lean exclusively upon the true God. That he may never be deprived of this practical truth, he testifies that he had made great proficiency in it. When he promises to become a publisher of God's wondrous works, his object in coming under this engagement is, that by his ingratitude he may not interrupt the course of the Divine beneficence.
Upon the truth here stated, he rests the prayer which he presents in the 18th verse, that he may not be forgotten in his old age. His reasoning is this: Since thou, O God! hast from the commencement of my existence given me such abundant proofs of thy goodness, wilt thou not stretch forth thy hand to succor me, when now thou seest me decaying through the influence of old age? And, indeed, the conclusion is altogether inevitable, that as God vouchsafed to love us when we were infants, and embraced us with his favor when we were children, and has continued without intermission to do us good during the whole course of our life, he cannot but persevere in acting toward us in the same way even to the end. Accordingly, the particle gm, gam, which we have translated still, here signifies therefore; it being David's design, from the consideration that the goodness of God can never be exhausted, and that he is not mutable like men, to draw the inference that he will be the same towards his people in their old age, that he was towards them in their childhood. He next supports his prayer by another argument, which is, that if he should fail or faint in his old age, the grace of God, by which he had been hitherto sustained, would at the same time soon be lost sight of. If God were immediately to withdraw his grace from us after we have but just tasted it slightly, it would speedily vanish from our memory. In like manner, were he to forsake us at the close of our life, after having conferred upon us many benefits during the previous part of it, his liberality by this means would be divested of much of its interest and attraction. David therefore beseeches God to assist him even to the end, that he may be able to commend to posterity the unintermitted course of the Divine goodness, and to bear testimony, even at his very death, that God never disappoints the faithful who betake themselves to him. By the generation and those who are to come, he means the children and the children's children to whom the memorial of the loving-kindness of God cannot be transmitted unless it be perfect in all respects, and has completed its course. He mentions strength and power as the effects of God's righteousness. He is, however, to be understood by the way as eulogising by these titles the manner of his deliverance, in which he congratulates himself; as if he had said, that God, in the way in which it was accomplished, afforded a manifestation of matchless and all-sufficient power.
19. And thy righteousness, O God! is very high. Some connect this verse with the preceding, and repeating the verb I will declare, as common to both verses, translate, And I will declare thy righteousness, O God! But this being a matter of small importance, I will not dwell upon it. David prosecutes at greater length the subject of which he had previously spoken. In the first place, he declares that the righteousness of God is very high; secondly, that it wrought mightily; and, finally, he exclaims in admiration, Who is like thee? It is worthy of notice, that the righteousness of God, the effects of which are near to us and conspicuous, is yet placed on high, inasmuch as it cannot be comprehended by our finite understanding. Whilst we measure it according to our own limited standard, we are overwhelmed and swallowed up by the smallest temptation. In order, therefore, to give it free course to save us, it behoves us to take a large and a comprehensive view -- to look above and beneath, far and wide, that we may form some due conceptions of its amplitude. The same remarks apply to the second clause, which makes mention of the works of God: For thou hast done great things. If we attribute to his known power the praise which is due to it, we will never want ground for entertaining good hope. Finally, our sense of the goodness of God should extend so far as to ravish us with admiration; for thus it will come to pass that our minds, which are often distracted by an unholy disquietude, will repose upon God alone. If any temptation thrusts itself upon us, we immediately magnify a fly into an elephant; or rather, we rear very high mountains, which keep the hand of God from reaching us; and at the same time we basely limit the power of God. The exclamation of David, then, Who is like thee? tends to teach us the lesson, that we should force our way through every impediment by faith, and regard the power of God, which is well entitled to be so regarded, as superior to all obstacles. All men, indeed, confess with the mouth, that none is like God; but there is scarce one out of a hundred who is truly and fully persuaded that He alone is sufficient to save us.