Do not speak in the hearing of a fool,
for he will despise the good sense of your words.
The proverb is almost comical in the picture it connotes. The hero/guide shouts words of instruction, only to be ignored by the fool who then lands in the hidden trap…which if filled with tigers!
But how does this work out in everyday life? First it would be helpful to identify the person who is the fool (so we make sure it is not us!). Derek Kidner, a wonderful pithy commentator, offers this insight:
"By derivation, it seems to mean one who is dull and obstinate; but it must always be remembered that [Proverbs] has in mind a man’s chosen outlook, rather than his mental equipment. We are shown the kĕsîl as he is first in himself, and second in society."
So we are looking for a person who in and of themselves has chosen to take such a foolish perspective on life, work, themselves, their relationships, hobbies, relative…you fill in the blank. Now they don’t have to have all of these flaws – one or two would sink a person. But here is the problem: The reader is cautioned about speaking in their hearing because they may despise the wisdom proffered. There are a few reasons for this: 1. the wisdom is wasted (no great harm with that); but 2. the fool may “discredit” the wisdom in front of others, thereby dulling the impact of how God is using you; or 3. the wisdom is not heard or well-regarded by the fool – and here there is a problem. If we as Christians are supposed to enrich the hearer with our words (cf. Prov. 16:24, 22:11; Eph. 4:25, 29; 2 Tim. 2:24), and, like Paul attempt to make every attempt to win others to the Lord (cf. 1 Cor. 9:19-22), then speaking wisdom at the wrong time may harden someone’s ears and heart, rather than being used by the Lord to encourage and draw them towards the God of all wisdom.
 Derek Kidner, Proverbs: An Introduction and Commentary, vol. 17, Tyndale Old Testament Commentaries (Downers Grove, IL: InterVarsity Press, 1964), 37.