etam vidyam adhigato
vinirjitya mrdhe ’suran
etam—this; vidyam—prayer; adhigatah—received; visvarupat—from the brahmana Visvarupa; sata-kratuh—Indra, the King of heaven; trailokya-laksmim—all the opulence of the three worlds; bubhuje—enjoyed; vinirjitya—conquering; mrdhe—in battle; asuran—all the demons.
King Indra, who performed one hundred sacrifices, received this prayer of protection from Visvarupa. After conquering the demons, he enjoyed all the opulences of the three worlds.
This mystical mantric armor given by Visvarupa to Indra, the King of heaven, acted powerfully, with the effect that Indra was able to conquer the asuras and enjoy the opulence of the three worlds without impediments. In this regard, Madhvacarya points out:
One must receive all kinds of mantras from a bona fide spiritual master; otherwise the mantras will not be fruitful. This is also indicated in Bhagavad-gita (4.34):
“Just try to learn the truth by approaching a spiritual master. Inquire from him submissively and render service unto him. The self-realized soul can impart knowledge unto you because he has seen the truth.” All mantras should be received through the authorized guru, and the disciple must satisfy the guru in all respects, after surrendering at his lotus feet. In the Padma Purana it is also said, sampradaya-vihina ye mantras te nisphala matah. There are four sampradayas, or disciplic successions, namely the Brahma-sampradaya, the Rudra-sampradaya, the Sri sampradaya and the Kumara-sampradaya. If one wants to advance in spiritual power, one must receive his mantras from one of these bona fide sampradayas; otherwise he will never successfully advance in spiritual life.
Thus end the Bhaktivedanta purports of the Sixth Canto, Eighth Chapter, of the Srimad-Bhagavatam, entitled “The Narayana-kavaca Shield.”
Link to this page: https://prabhupadabooks.com/sb/6/8/42