Chapter 26:4-5 Answer not a fool according to his folly, lest thou also be like unto him.
Answer a fool according to his folly, lest he be wise in his own conceit.
To “answer a fool according to his folly” means to descend to his level of reasoning, coarse anger and abuse; in 5 it is to say the right word to him at the right time, to expose his lack of wisdom, not by a telling him what is beyond his comprehension because it will be useless to him. Answer a fool in your own wisdom and not in his foolishness. Don't come down to his level!