Ecclesiastes 10:1-3

Dead flies cause the ointment of the apothecary to send forth a stinking savour: so doth a little folly him that is in reputation for wisdom and honour. A wise man's heart is at his right hand; but a fool's heart at his left. Yea also, when he that is a fool walketh by the way, his wisdom faileth him, and he saith to every one that he is a fool.