Since one cannot visually experience the presence of the Supersoul, He appears before us as a liberated devotee. Such a spiritual master is none other than Krishna himself.
A. C. Bhaktivedanta Swami PrabhupadaYou should not be carried away by the dictation of the mind, but the mind should be carried by your dictation.
A. C. Bhaktivedanta Swami PrabhupadaThe spiritual master and Krishna are two parallel lines. The train, on two tracks, moves forward. The spiritual Master and Krishna are like these two tracks. They must be served simultaneously. Krishna helps one to find bona fide Spiritual Master and bona fide Spiritual Master helps one to understand Krishna. If one does not get bona fide Spiritual Master, then how he can ever understand Krishna ? You cannot serve Krishna without Spiritual Master, or serve just Spiritual Master without serving Krishna. They must be served simultaneously.
A. C. Bhaktivedanta Swami PrabhupadaA disciple serves the spiritual master with the sole purpose of getting instructions from him.
A. C. Bhaktivedanta Swami Prabhupada