Taking to Krṣṇa Consciousness
79
Perfection of duty can be tested by seeing whether the Supreme Lord is satisfied by its execution. The Supreme Lord's satisfaction can be tested by the Lord's representative, the spiritual master. Therefore it is important to seek out a real representative of the Supreme Personality of Godhead and work under him. If he is satisfied, then we should know that the Supreme Lord is also satisfied. That is explained by Viśvanātha Cakravartī Thākura:
yasya prasādād bhagavat-prasādo 
    yasyāprasādān na gatiḥ kuto'pi 
    dhyāyam stuvams tasya yaśas tri-sandhyam 
    vande guroḥ śrī-caraṇāravindam
“By the mercy of the spiritual master one is benedicted by the mercy of Krṣṇa. Without the grace of the spiritual master no one can make any advancement. Therefore I should always remember the spiritual master. At least three times a day I should offer my respectful obeisances unto the lotus feet of my spiritual master.” (Śrī  Gurvaṣṭakam , Verse 8)
The spiritual master is the representative of the Supreme Lord. How does he become the representative? If one says that such and such an object is a pair of spectacles, and if he teaches his disciple in that way, there is no mistake as to the identity of the object. The spiritual master is he who has captured the words of a particular discipline succession. In the case given, the key word is “spectacles”—that’s all. The spiritual master does not have to say anything beyond that. This is the qualification.