Rotten wood cannot be carved.

Related:

• Rotten wood cannot be carved. -- Confucius, "Analects",
  Book 5, Ch....
• A closed mind is like a closed book;
  just a block of wood Chinese...
• He who cannot agree with his enemies is controlled by them.
  Chinese...
• So long as a man is angry he cannot be in the right.
  Chinese...
• When I was your age we carved our transistors out
  of wood...
• A razor may be sharper than an ax, but it cannot cut wood.
  African(Annang)...
• The universe is ruled by letting things take their course.
  It cannot be ruled by interfering. -- Chinese...