How the spiritual master’s grace is received through the ears
The favor of the spiritual master is not
received through any other part of the body but the ears. This does not
mean, however, that the spiritual master gives a particular type of
mantra through the ears in exchange for some dollars and if the man
meditates on that he achieves perfection and becomes God within six
months. Such reception through the ears is bogus. The real fact is that a
bona fide spiritual master knows the nature of a particular man and what
sort of duties he can perform in Krsna consciousness, and he instructs
him in that way. He instructs him through the ear, not privately, but
publicly. “You are fit for such and such work in Krsna consciousness. You
can act in this way.”
Srimad Bhagavatam 3.22.7 purport