Charles H. Spurgeon on Psalms 71:18

Now also when I am old and grey headed, O God, forsake me not. There is something touching in the sight of hair whitened with the snows of many a winter: the old and faithful soldier receives consideration from his king, the venerable servant is beloved by his master. When our infirmities multiply, we may, with confidence, expect enlarged privileges in the world of grace, to make up for our narrowing range in the field of nature. Nothing shall make God forsake those who have not forsaken him. Our fear is lest he should do so; but his promise kisses that fear into silence. Until I have shewed thy strength unto this generation. He desired to continue his testimony and complete it; he had respect to the young men and little children about him, and knowing the vast importance of training them in the fear of God, he longed to make them all acquainted with the power of God to support his people, that they also might be led to walk by faith. He had leaned on the almighty arm, and could speak experimentally of its all sufficiency, and longed to do so ere life came to a close. And thy power to every one that is to come. He would leave a record for unborn ages to read. He thought the Lord's power to be so worthy of praise, that he would make the ages ring with it till time should be no more. For this cause believers live, and they should take care to labour zealously for the accomplishment of this their most proper and necessary work. Blessed are they who begin in youth to proclaim the name of the Lord, and cease not until their last hour brings their last word for their divine Master.