Ecclesiastes 10:8-11

He who digs a pit may fall into it, and a serpent may bite him who breaks through a wall. He who quarries stones may be hurt by them, and he who splits logs may be endangered by them. If the axe is dull and he does not sharpen its edge, then he must exert more strength. Wisdom has the advantage of giving success. If the serpent bites before being charmed, there is no profit for the charmer.