Albert Barnes Commentary Psalms 71:9

"Cast me not off in the time of old age; Forsake me not when my strength faileth." — Psalms 71:9 (ASV)

Cast me not off in the time of old age - This means when old age comes with its infirmities, its weaknesses, and its trials.

It is when my strength fails me; when my eyes grow dim; when my knees totter; when my friends have died; when I am no longer able to work for my support; when the buoyant feelings of earlier years are gone; when my old companions and associates have passed away, and I am left alone.

You who watched over me in infancy, who guarded me in childhood and youth, who have defended me in manhood, who have upheld me in days of sickness, danger, bereavement, and trouble—do not leave me when, in advanced years, I have special need of your care.

Do not leave me when I have reason to anticipate that troubles I have never known before may come upon me in that season of my life; when I will not have the strength, the buoyancy, the elasticity, the ardor, or the vitality of other years to enable me to meet those troubles; and when I will have none of the friends to cheer me whom I had in the earlier periods of my life.

It is not unnatural or improper for a man who sees old age approaching to pray for special grace and strength. This is to enable him to meet what he cannot prevent and what he cannot help but dread. For who can look upon the infirmities of old age coming upon himself without sad and pensive feelings?

Who would wish to be an old man? Who can look upon a man tottering with years and broken down with infirmities—a man whose sight and hearing are gone, a man who is alone amidst the graves of all the friends he had in early life, a man who is a burden to himself and to the world, a man who has reached the "last scene of all, that ends the strange eventful history," that scene of:

"Second childishness and mere oblivion,
Sans teeth, sans eyes, sans taste, sans everything."

That scene when one can say:

"I have lived long enough; my way of life
Is fallen into the sear, the yellow leaf;
And that which should accompany old age,
As honor, love, obedience, troops of friends,
I must not look to have."

Who can think of all this and not pray for special grace for himself, should he live to see those days of infirmity and weakness? And who, in view of such infirmities, can fail to see the wisdom of seeking God's favor in early years? (Compare to Ecclesiastes 12:1-6.)

Forsake me not when my strength faileth - As I may expect it to do when I grow old. A man can store up nothing better for the infirmities of old age than the favor of God, sought by earnest prayer in the days of his youth and his mature years.