Proverbs 24:8 He that deviseth to do evil shall be called a mischievous person. 

This verse moves from the fool who cannot formulate wise counsel to the person who deliberately devises evil. The word deviseth indicates planning, scheming, or deliberately forming a course of action. There is a difference between committing an impulsive wrong and carefully planning to do wrong.

This person does not merely stumble into sin. He thinks about it, plans it, and looks for an opportunity to carry it out. Such a person becomes known for his schemes.

‘Shall be called a mischievous person.’ The idea is that he becomes recognised as a schemer or deviser of evil. His reputation eventually catches up with his character. A person may hide his intentions for a time, but repeated conduct eventually reveals who he is.

This is a serious warning because the mind can become trained either toward righteousness or toward wickedness. The wise person asks: “How can I do what is right?” The wicked person asks: “How can I get what I want?”