Every workman knows the necessity of keeping his tools in a good state of repair, for ‘if the iron be blunt, and he do not whet the edge, then must he put to more strength.’ If the workman lose the edge from his adze, he knows that there will be a greater draught upon his energies, or his work will be badly done. Michael Angelo, the elect of the fine arts, understood so well the importance of his tools, that he always made his own brushes with his own hands, and in this he gives us and illustration of the God of grace, who with special care fashions for himself all true ministers. It is true that the Lord, like Quintin Matsys in the story of the Antwerp well-cover, can work with the faultiest kind of instrumentality, as he does when he occasionally makes very foolish preaching to be useful in conversion; and he can even work without agents, as he does when he saves men without a preacher at all, applying the word directly by his Holy Spirit; but we cannot regard God’s absolutely sovereign acts as a rule for our action. He may, in his own absoluteness, do as pleases him best, but we must act as his plainer dispensations instruct us; and one of the facts which is clear enough is this, that the Lord usually adapts means to ends, from which the plain lesson is, that we shall be likely to accomplish most when we are in the best spiritual condition; or in other words, we shall usually do our Lord’s work best when our gifts and graces are in good order, and we shall do worst when they are most out of trim.
Lectures to My Students (Pasadena, TX; Pilgrim; 1990) p. 1