(Click to enlarge photo of Srila Prabhupada and disciples)
"Even though we may not have the fortune to contact the Supreme Lord personally, the Lord’s representative is as good as the Lord Himself because such a representative does not say anything unless it is spoken by the Supreme Personality of Godhead. Śrī Caitanya Mahāprabhu therefore gives a definition of guru. Yāre dekha, tāre kaha 'kṛṣṇa'-upadeśa: (CC Madhya 7.128) the bona fide guru is he who advises his disciples exactly in accordance with the principles spoken by Kṛṣṇa. The bona fide guru is he who has accepted Kṛṣṇa as guru. This is the guru-paramparā system. The original guru is Vyāsadeva because he is the speaker of Bhagavad-gītā and Śrīmad-Bhāgavatam, wherein everything spoken relates to Kṛṣṇa. Therefore guru-pūjā is known as Vyāsa-pūjā. In the final analysis, the original guru is Kṛṣṇa, His disciple is Nārada, whose disciple is Vyāsa, and in this way we gradually come in touch with the guru-paramparā. One cannot become a guru if he does not know what the Personality of Godhead Kṛṣṇa or His incarnation wants. The mission of the guru is the mission of the Supreme Personality of Godhead: to spread Kṛṣṇa consciousness all over the world."
(Śrīmad-Bhāgavatam 8.24.48, Purport)
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