Ecclesiastes 10:9-11

New Catholic Bible

⁹ Whoever quarries stones will be hurt by them,
    and whoever chops wood places himself at risk.
¹⁰ If an ax becomes dull from lack of sharpening,
    then one must exert greater strength,
    but skill helps one to succeed.
¹¹ If a snake bites because it has not been charmed,
    there is no profit for the charmer.