Leader teaches by example

People in general always require a leader who can teach the public by practical behavior. A leader cannot teach the public to stop smoking if he himself smokes. Lord Caitanya said that a teacher should behave properly before he begins teaching. One who teaches in that way is called acarya, or the ideal teacher. Therefore, a teacher must follow the principles of sastra (scripture) to teach the common man.

(Srila Prabhupada, Bhagvad Gita-As It Is, 3.21 Purport)