Bede

He who thinks to do evil, shall be called a fool. Do not think that he whom you see to be dull and slow-witted should be considered a fool, he clearly shows that he should be called a fool who even consents to the suggestions of sin in thought, even if he seems sharp in intellect; but not him who, although he appears dull in sense, resolved to obey the commands of God, which he could learn.

Commentary on Proverbs ↗