"As I have repeatedly said, that Krishna Consciousness is developed by following two parallel lines, means service of Krishna, and service of the Spiritual Master. This is the secret of success.
"The Spiritual Master must be bona fide, that is, he must come down from a bona fide Spiritual Master and must act according to the directions of the Spiritual Master, and by doing so, he gives proper directions about Krishna and the devotees serve Krishna under the direction of such Spiritual Master, and Krishna accepts service, and in this way the whole thing becomes beautiful and successful.
"I am very much pleased that you are following the same principle and there is no doubt that you will develop more and more in the service of Krishna. I always pray to Krishna for your advancement, and what I can do more than this."
(Srila Prabhupada letter, February 20, 1968)