Ecclesiastes 10:1-3

New Century Version

10 Dead flies can make even perfume stink.
    In the same way, a little foolishness can spoil wisdom.
² The heart of the wise leads to right,
    but the heart of a fool leads to wrong.
³ Even in the way fools walk along the road,
    they show they are not wise;
    they show everyone how stupid they are.