From J. Gresham Machen's Faith and Works:
So in the midst of a practical world, the Christian exhibits a practical life of love — a busy life of helpfulness, feeding the hungry, giving drink to the thirsty, receiving the strangers, clothing the naked, visiting the sick and the prisoners. And all that accomplished not by his own unaided efforts, not even merely by his own faith, but by the great object of his faith, the all-powerful God.
The Christian preacher, then, comes before the world with a great alternative. Shall we continue to depend upon our own efforts, or shall we receive by faith the power of God? Shall we content ourselves with the materials which this world affords, seeking by endlessly new combinations to produce a building that shall endure; or shall we build with the materials that have no flaw? Shall we give men new motives, or ask God to give them a new power? Shall we improve the world, or pray God to create a new world? The former alternatives have been tried and found wanting: the best of architects can produce no enduring building when all the materials are faulty; good motives are powerless when the heart is evil. Struggle as we may, we remain just a part of this evil world until, by faith, we cry: “Not by might, nor by power, but by Thy Spirit. O Lord of Hosts.”