Jerome : "If a blade is blunt and one has not sharpened the edge, nevertheless it strengthens the warriors. Wisdom is a more powerful skill. "If someone, he says, has seen himself lose knowledge of the Scriptures through negligence, and the shrewdness of his intelligence has been blunted, nonetheless he remains disturbed, and he would be just as he had been when he started. But it happens, meanwhile, that he that has a little knowledge is led into pride and stops learning and reading, and little by little takes away from that which now adds nothing to him. Thus the heart of the pupil remains empty, and a blade that has been sharpened is made blunt. For rest and laziness are like a kind of rust of wisdom. So then if anyone has suffered this, let him not despair the remedy for his health, but let him go to his teacher and be instructed again by him, and then after much toil and hard work, and a great deal of much sweat, he will be able to regain that wisdom that he had lost. And this is what is said in the Hebrew more to the point: he will be strengthened by might, that is, by toil, by sweat, by hard work, and daily reading, then wisdom will follow suit, and his toil will come to an end, so that he might be able to receive wisdom once more. — Commentary on Ecclesiastes