Ecclesiastes 10:9-11

Revised Standard Version

⁹ He who quarries stones is hurt by them;
    and he who splits logs is endangered by them.
¹⁰ If the iron is blunt, and one does not whet the edge,
    he must put forth more strength;
    but wisdom helps one to succeed.
¹¹ If the serpent bites before it is charmed,
    there is no advantage in a charmer.