"So the spiritual master is not self-made. It is not that if anyone comes before you and bluffs you that 'I have attained spiritual perfection, and I have realized something by some method.' No. The spiritual master, bona fide spiritual, means he has to receive the power from authority. Otherwise it is useless. No. It is not that one can become spiritual master overnight. He has to take the power from his spiritual master. Therefore it is called prāptasya. Prāptasya means one who has obtained, one who has got the merciful blessings of his spiritual master.
We should always remember that the spiritual master is in the disciplic succession. The original spiritual master is the Supreme Personality of Godhead. He blesses His next disciple, just like Brahmā. Brahmā blesses his next disciple, just like Nārada. Nārada blesses his next disciple, just like Vyāsa. Vyāsa blesses his next disciple, Mādhvācārya. Similarly, the blessing is coming. Just like royal succession—the throne is inherited by disciplic or hereditary succession—similarly, this power from the Supreme Personality of Godhead has to receive. Nobody can preach, nobody can become a spiritual master, without obtaining power from the right source. Therefore the very word, it is stated here, prāptasya. Prāptasya means 'one who has obtained.' Prāptasya kalyāṇa. What he has obtained? Kalyāṇa. Kalyāṇa means auspicity. He has received something which is auspicious for all the humankind. Prāptasya kalyāṇa-guṇārṇavasya.
Here is another example: guṇārnava. Arṇava means ocean, and guṇa means spiritual qualities. Just like the same example is going on. It is very nice poetry. There is nice rhetorics and metaphor. The example is set, blazing fire, and it is to be extinguished with the cloud. And wherefrom the cloud comes? Similarly, wherefrom the spiritual master receives the mercy? The cloud receives his potency from the ocean. Therefore the spiritual master also receives his power from the ocean of spiritual qualities, that is, from the Supreme Personality of Godhead. So prāptasya kalyāṇa-guṇārṇavasya. Such kind of spiritual master one has to accept, and vande guroḥ śrī-caraṇāravindam, and one has to offer his respectful obeisances to such authorized spiritual master."
(Srila Prabhupada Lecture, Los Angeles, January 2, 1969)