There was once a rich man in the State of Song. After a heavy downpour, his wall began to crumble.
"If you don't mend that wall," warned his son, "a thief will get in."
An old neighbor gave him the same advice, but the man paid no attention.
That very night, a great deal of his money was indeed stolen. Afterwards, the rich man constantly praised his son's intelligence, but he suspected his old neighbor of being the thief.