From Strength to Strength part II

"From Strength to Strength" Psalm 84:7

It is divine, not human strength, and it is strength which is wholly divine and in no sense or measure human. It is an exchange of strength in which we have surrendered all our power and received instead the divine power and enabling. This glorious exchange of strength is vividly set forth in Isaiah, chapter 40: "He giveth power to the faint, and to them that have no might He increaseth strength. Even the youths shall faint and be weary, and the young men shall utterly fall, but they that wait upon the Lord shall exchange their strength." That is to say, the strongest human strength, the manhood of young men, the vigor and vitality of youth, shall be wholly inadequate for the exigencies of Christian life and conflict, and it is not until these have failed that God has room to display the resources of His omnipotence. When we become "faint," then He giveth His power, and when we have "no might," then He "increaseth strength," that is, gives yet more because of our utter helplessness. Waiting on the Lord, we let our strength go and take His instead, and so renew or exchange our strength.