John Calvin 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 my old age. Having just declared that God had been the protector of his life at his birth, afterwards his foster-father in his childhood, and the guardian of his welfare during the whole course of his past existence, David, now worn out with age, casts himself anew into the fatherly bosom of God.

In proportion as our strength fails us—and then necessity itself impels us to seek God—in the same proportion should our hope in the willingness and readiness of God to help us become strong. David’s prayer, in short, amounts to this: “You, O Lord, who have sustained me vigorous and strong in the flower of my youth, do not forsake me now, when I am decayed and almost withered, but the more I stand in need of your help, let the decrepitude and infirmities of age move you to compassionate me the more.” From this verse, expositors, not without good reason, conclude that the conspiracy of Absalom is the subject of this psalm.

And certainly it was a horrible and tragic spectacle, which tended to lead, not only the common people, but also those who excelled in authority, to turn away their eyes from him, as they would from a detestable monster, when the son, having driven his father from the kingdom, pursued him even through the very deserts to put him to death.