"The way in which most of the things we use are serviceable to us and answer their end is in their being strained, or hard-pressed, or violently agitated. Thus the way in which the bow answers its end is in hard straining of it to shoot the arrow and do the execution; the bow that won't bear straining is good for nothing, So it is with a staff that a man walks with: it answers its end in being hard-pressed. So it is with many of the members of our bodies, our teethc, our feet, etc. They are useful and answer their end by some violent straining, pressure, agitation, collision or impulsion, and they that are so weak not to bear the trial of such useage are good for nothing.
Here is a lively representation of the way in which true and sincere saints (which are often in scripture represented as God's instruments or utensils) answer God's end, and serve and glorify him in it: by enduring temptation, going through hard labor, suffering, or self-denial or such service or strains hard upon nature and self. Hypocrites are like a broken tooth, a foot out of joint, or broken staff, a deceitful bow, which fail when pressed or strained."
Jonathan Edwards, Image of Divine Things