For which cause - With such an object in view, and sustained by such elevated purposes and desires. The sense is, that the purpose of trying to save as many as possible would make toil easy, privations welcome, and would be so accompanied by the grace of God, as to gird the soul with strength, and fill it with abundant consolations.
We faint not - For an explanation of the word used here, see the note on 2 Corinthians 4:1. We are not exhausted, desponding, or disheartened. We are sustained, encouraged, emboldened by having such an object in view.
But though our outward man perish - By outward man, Paul evidently means the body. By using the phrases, “the outward man,” and the “inward man,” he shows that he believed that man was made up of two parts, body and soul. He was no materialist. He has described two parts as constituting man, so distinct: that while the one perishes, the other is renewed; while the one is enfeebled, the other is strengthened; while the one grows old and decays, the other renews its youth and is invigorated. Of course, the soul is not dependent on the body for its vigor and strength, since it expands while the body decays; and of course the soul may exist independently of the body, and in a separate state.
Perish - Grows old; becomes weak and feeble; loses its vigor and elasticity under the many trials which we endure, and under the infirmities of advancing years. It is a characteristic of the “outer man,” that it thus perishes. Great as may be its vigor, yet it must decay and die. It cannot long bear up under the trials of life, and the wear and tear of constant action, but must soon sink to the grave.
Yet the inward man - The soul; the undecaying, the immortal part.
Is renewed - Is renovated, strengthened, invigorated. His powers of mind expanded; his courage became bolder; he had clearer views of truth; he had more faith in God. As he drew nearer to the grave and to heaven, his soul was more raised above the world, and he was more filled with the joys and triumphs of the gospel. The understanding and the heart did not sympathize with the suffering and decaying body; but, while that became feeble, the soul acquired new strength, and was fitting for its flight to the eternal world. This verse is an ample refutation of the doctrine of the materialist, and proves that there is in man something that is distinct from decaying and dying matter, and that there is a principle which may gain augmented strength and power, while the body dies; compare note, Romans 7:22.
Day by day - Constantly. There was a daily and constant increase of inward vigor. God imparted to him constant strength in his trials, and sustained him with the hopes of heaven, as the body was decaying, and tending to the grave. The sentiment of this verse is, that in an effort to do good, and to promote the salvation of man, the soul will be sustained in trials, and will be comforted and invigorated even when the body is weary, grows old, decays, and dies. It is the testimony of Paul respecting his own experience; and it is a fact which has been experienced by thousands in their efforts to do good, and to save the souls of people from death.