The devotee knelt to be initiated into discipleship. The guru whispered the sacred mantra into his ear, warning him not to reveal it to anyone.
What will happen if I do? asked the devotee.
Said the guru, Anyone you reveal the mantra to will be liberated from the bondage of ignorance and suffering, but you yourself will be excluded from discipleship and suffer damnation.
No sooner had he heard those words, than the devotee rushed to the marketplace, collected a large crowd around him, and repeated the sacred mantra for all to hear.
The disciples later reported this to the guru and demanded that the man be expelled from the monastery for his disobedience.
The guru smiled and said, He has no need of anything I can teach. His action has shown him to be a guru in his own right.
This is from The Heart of the Enlightened, a book of spiritual stories by Anthony de Mello.