This is a well researched, nicely written article by Sriman Hayagriva Prabhu, with many quotes from Srila Prabhupada’s books. Worth the read!
The Spiritual Master: Emissary of the Supreme Person
By Hayagriva Dasa Adhikari
Published in Back to Godhead Magazine 1970, Vol.1, No.38
brahmāṇḍa bhramite kona bhāgyavān jīva
guru-kṛṣṇa-prasāde pāya bhakti-latā-bīja
“According to their karma, all living entities are wandering throughout the entire universe. Some of them are being elevated to the upper planetary systems, and some are going down into the lower planetary systems. Out of many millions of wandering living entities, one who is very fortunate gets an opportunity to associate with a bona fide spiritual master by the grace of Kṛṣṇa. By the mercy of both Kṛṣṇa and the spiritual master, such a person receives the seed of the creeper of devotional service.”(Śrī Caitanya-caritāmṛta: Madhya-līlā 19.151)
His Divine Grace A.C. Bhaktivedanta Swami, Srila Prabhupada, once said that religion without philosophy is fanaticism and philosophy without religion is mental speculation. For a sincere student engaged in God realization, major philosophical points should be understood in the light of the guru, scripture and practical devotional service. One of the first points to understand is the position of the spiritual master. How is he related to Krsna? Is he Krsna? Is he an ordinary man? How should the disciple approach him? How can one know that the spiritual master is bona fide? What is the duty of the spiritual master? What are his symptoms? These and other questions concerning the spiritual master and Krsna are discussed herein by way of authoritative evidence compiled from the writings of Srila Prabhupada, the spiritual master himself.
In addition to rendering devotional service to Krsna through the spiritual master, the student should come to a philosophical understanding based on scripture of his own identity and the identity of the Supreme Person, Sri Krsna, and His emissary, the bona fide spiritual master. This understanding should correlate with the basic teachings of the spiritual master and other great saints and sages.
The Hare Krishna Movement 