Proverbs 24:7 Wisdom is too high for a fool: he openeth not his mouth in the gate.
8 He that deviseth to do evil shall be called a mischievous person.
9 The thought of foolishness is sin: and the scorner is an abomination to men.
Wisdom is a gift from God but a fool is too busy to even listen to someone who is trying to help him gain some wisdom. Because he could care less for wisdom he is not allowed to sit at the gate where people enter the city. A person who likes to do evil is always planning ways to beat people out of things instead of working for what he has. He is a genius at plotting schemes to swindle people of their goods. The word of God says if we desire to sin in our heart we have sinned already. The heart will be judged more than the actions we commit. The scourer or rejecters of Christian principals and that turn their backs on God are a terrible reproach and abomination to God and the righteous. We see in these verses that there are some who will never listen to anyone that tries to get them to change their ways but it is still our job to try to witness to as many as we can.