Aesop
The Crab and Its Mother
A CRAB said to her son, "Why do you walk so one-sided, my child?
It is far more becoming to go straight forward." The young Crab
Replied: "Quite true, dear Mother; and if you will show me the
Straight way, I will promise to walk in it." The Mother tried in
Vain, and submitted without remonstrance to the reproof of her
Child.

Example is more powerful than precept.