(18) Now also when.—Literally, yea, even to old age and grey hairs. Psalm 129:1 shows that this may be a national as well as an individual prayer.

Thy strength.—Literally, thine arm, the symbol of power. (Comp. Isaiah 52:10; Isaiah 53:1, &c)

Unto this generation.—Literally, to a generation, explained by the next clause to mean, to the coming generation.

Psalm 71:18. Now also when I am old, &c., forsake me not — Do not abandon the care of me when I need it most: but continue the same kindness to me in my declining years which I experienced when I was a youth. Those that have been taught of God from their youth, and have made it the business of their lives to honour him, may be sure he will not leave them when they are old and gray-headed, will not leave them helpless and comfortless, but will make the evil days of old age their best days, and such as they shall have reason to say they have pleasure in. Until I have showed thy strength — By my own experience of its being exerted in fresh instances in my behalf; unto this generation — To which I owe peculiar duties, and which I desire to serve according to thy will, Acts 13:36; and thy power to every one that is to come — To all future generations, by leaving my observations upon it on record for their benefit. Thus, as David acknowledges that “it was the God of Israel who taught him, as a warrior, to conquer, and as a psalmist, to declare the wondrous works of his great benefactor; so he requests to be preserved in his old age, until, by completing his victories, and his Psalms composed to celebrate them, he had showed the strength and power of God,” not only to his cotemporaries, “but to all that should arise in after times, and chant those divine hymns in the assemblies of the faithful, throughout all ages.” In like manner, “if St. Paul wish to have his life continued on earth, it is only that he may edify the church and glorify God. Otherwise it is far better, says he, to depart and be with Christ.” — Horne. In imitation of these, and such like excellent examples, as long as we live we ought to be endeavouring to glorify God, and edify one another; and those that have had the largest and longest experience of the goodness of God to them, should improve their experience for the good of their friends. And it is a debt which the old disciples of Christ owe to the succeeding generations, to leave behind them a solemn testimony to the power, and pleasure, and advantage of religion, and the truth of God’s promises.

71:14-24 The psalmist declares that the righteousness of Christ, and the great salvation obtained thereby, shall be the chosen subject of his discourse. Not on a sabbath only, but on every day of the week, of the year, of his life. Not merely at stated returns of solemn devotion, but on every occasion, all the day long. Why will he always dwell on this? Because he knew not the numbers thereof. It is impossible to measure the value or the fulness of these blessings. The righteousness is unspeakable, the salvation everlasting. God will not cast off his grey-headed servants when no longer capable of labouring as they have done. The Lord often strengthens his people in their souls, when nature is sinking into decay. And it is a debt which the old disciples of Christ owe to succeeding generations, to leave behind them a solemn testimony to the advantage of religion, and the truth of God's promises; and especially to the everlasting righteousness of the Redeemer. Assured of deliverance and victory, let us spend our days, while waiting the approach of death, in praising the Holy One of Israel with all our powers. And while speaking of his righteousness, and singing his praises, we shall rise above fears and infirmities, and have earnests of the joys of heaven. The work of redemption ought, above all God's works, to be spoken of by us in our praises. The Lamb that was slain, and has redeemed us to God, is worthy of all blessing and praise.Now also when I am old and grey-headed - Margin, "unto old age and grey hairs." This does not necessarily mean that he was then actually old and grey-headed, but it would imply that he was approaching that period, or that he had it in prospect. The time of youth was past, and he was approaching old age. The literal rendering would be, "And also unto old age and grey hairs, do not forsake me." This is the prayer of one who had been favored in youth, and in all his former course of life, and who now asked that God would continue his mercy, and not forsake him when the infirmities of age drew on.

Forsake me not - Still keep me alive. Give me health, and strength, and ability to set forth thy praise, and to make known thy truth. See the notes at Psalm 71:9.

Until I have showed thy strength - Margin, as in Hebrew, "thine arm." The arm is the instrument by which we execute a purpose, and it thus becomes a symbol of strength.

Unto this generation - literally, "to a generation." The reference is to the generation then living; that is, the generation which had come on the stage since he had reached manhood - the generation - the new generation - which one who is approaching old age sees engaged in the active scenes of life, cultivating the fields, filling the offices, constructing the bridges and roads, manning the ships, occupying the dwellings, instead of those with whom he was formerly associated, and who are now in their graves. His own generation - the companions of his own early years - had passed away. He had lived to speak to a new generation, and he was desirous that they should start on the journey of life with the advantage of his experience, as of one that had gone before. Each generation "may" thus enter on life with all the accumulated wisdom of the past; that is, as wise as those had become who had themselves had the experience, and treasured up results from the observations, of a long life.

Society thus makes progress. One generation becomes wiser and better than the one which went before it, and the experience of all ages thus accumulates as the world advances, enabling a future age to act on the results of all the wisdom of the past. Man thus differs from the inferior creation. The animals, governed by instinct alone, make no progress. Compare the notes at Psalm 49:13. They profit neither by the wisdom, nor the follies of the past. The first robin built its nest of the same materials, and with as much art, as the robin does now; the first stock of bees constructed their cells with as nice and accurate adaptations, with mathematical precision as complete, as a swarm of bees will do now. Neither the bird nor the bee has learned anything by experience, by study, or by observation - nor lays up, to transmit to future generations of birds or bees, the results of its own sagacity or observation.

Not so with man. The result of the experiences of one generation goes into the general experience of the world, and becomes its capital; a new thought, or a new invention struck out by some splendid genius, becomes the common property of the race; and society, as it rolls on, gathers up all these results, as the Ganges or the Mississippi, rolling on to the ocean, gathers into one mighty volume all the waters that flow in a thousand streams, and all that come from rivulets and fountains, however remote. It is this which makes the life of "a man" so valuable in this world; this which makes it so desirable for a man, even when approaching old age, yet to live a little longer, for, as the fruit of his experience, his observation, his ripe wisdom, his acquired knowledge, he may yet suggest something, by writing or otherwise, which may add to the intelligence of the world; some principle which may be elaborated and perfected by the coming age.

And thy power - Thy greatness; majesty; glory.

To every one that is to come - To all future generations. That I may state truths which may benefit future ages. He who suggests one truth which the world was not in possession of before, is a benefactor to mankind, and will not have lived in vain, for that truth will do something to set the race forward, and to make the world better and happier. It is not a vain thing, then, for a man to live; and every one should endeavor "so" to live that the world may not be the worse - or may not go backward - by his living in it, but that it may be the wiser and the better: not merely so that it may keep on the same level, but that it may rise to a higher level, and start off on a new career.

17-21. Past experience again encourages.

taught me, &c.—by providential dealings.

Thy strength; either,

1. This further act or instance of thy strength. Or rather,

2. Thy great power, which will more eminently appear in this than it hath done in former deliverances, as my danger is now greater, because this is a civil war, and the generality of mine own people are engaged against me, and my forces are very inconsiderable to theirs, and without thy help my case is desperate.

To every one that is to come, i.e. to all succeeding generations, to whom I will leave a lasting monument of this glorious example of all-sufficiency, such as this Psalm is.

Now also, when I am old and grayheaded, O God, forsake me not,.... A repetition of his request, Psalm 71:9; with a reason annexed to it, suggested in the following words:

until I have showed thy strength unto this generation; or, "thine arm" (e); which sometimes the Messiah, Isaiah 53:1; who is the power of by whom he made the worlds, and in whom all things consist; and who has wrought out the salvation people; and is the arm on which they lean, and they are upheld. And the psalmist may be thought to desire that he might be continued a little longer, and be favoured with the presence of God, and the influences of his Spirit and grace; that he might show forth in prophecy, both by word and writing, to the men of the then present age, more things concerning the person, office, and grace of Christ; his sufferings, death, resurrection from the dead, and session at the right hand of God; things which are spoken of in the book of Psalms. Sometimes the arm of the Lord denotes his power and strength, Psalm 44:3; and so it may be taken here; and the next clause seems to be an explanation of it:

and thy power; or "even thy power",

to everyone that is to come; that is, to come into the world, that is to be born into it; namely, the power of God, not only in creating all things out of nothing, and supporting what is made; but in the redemption of men, in the conversion of sinners, and in the preservation of the saints, and in enabling them to hold on and out unto the end: and which is shown forth by the psalmist in what he has committed to writing; and which continue, and will continue, to the end of the world, for the instruction of those that come into it; see Psalm 22:31.

(e) "brachium tuum", V. L. Pagninus, Montanus, Tigurine version, Junius & Tremellius, Piscator, &c.

{m} Now also when I am old and grayheaded, O God, forsake me not; until I have shewed thy strength unto this generation, and thy power to every one that is to come.

(m) He desires that as he has begun, he would so continue his benefits, that his liberality may have perfect praise.