Ecclesiastes 10:9-11

New Revised Standard Version Catholic Edition

⁹ Whoever quarries stones will be hurt by them;
    and whoever splits logs will be endangered by them.
¹⁰ If the iron is blunt, and one does not whet the edge,
    then more strength must be exerted;
    but wisdom helps one to succeed.
¹¹ If the snake bites before it is charmed,
    there is no advantage in a charmer.