Ecclesiastes 10:8-10

Revised Standard Version

⁸ He who digs a pit will fall into it;
    and a serpent will bite him who breaks through a wall.
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.