A rod is for the back of him - He that can learn, and will not learn, should be made to learn. The rod is a most powerful instrument of knowledge. Judiciously applied, there is a lesson of profound wisdom in every twig.
i. e., The wisdom of the wise is seen in the words that issue from his lips; the folly of the fool is not only seen in his speech, but brings upon him the chastisement which he well deserves.