Oṁ namo bhagavate vāsudevāya is known as the dvādaśākṣara-mantra. This mantra is chanted by Vaiṣṇava devotees, and it begins with praṇava, or oṁkāra. There is an injunction that those who are not brāhmaṇas cannot pronounce the praṇava mantra. But Dhruva Mahārāja was born a kṣatriya. He at once admitted before Nārada Muni that as a kṣatriya he was unable to accept Nārada's instruction of renunciation and mental equilibrium, which are the concern of a brāhmaṇa. Still, although not a brāhmaṇa but a kṣatriya, Dhruva was allowed, on the authority of Nārada, to pronounce the praṇava oṁkāra. This is very significant. Especially in India, the caste brāhmaṇas object greatly when persons from other castes, who are not born in brāhmaṇa families, recite this praṇava mantra. But here is tacit proof that if a person accepts the Vaiṣṇava mantra or Vaiṣṇava way of worshiping the Deity, he is allowed to chant the praṇava mantra. In Bhagavad-gītā the Lord personally accepts that anyone, even one of a low species, can be elevated to the highest position and go back home, back to Godhead, simply if he worships properly.
The prescribed rules, as stated here by Nārada Muni, are that one should accept the mantra through a bona fide spiritual master and hear the mantra in the right ear. Not only should one chant or murmur the mantra, but in front of him he must have the Deity, or physical form of the Lord. Of course, when the Lord appears it is no longer a physical form. For example, when an iron rod is made red-hot in a fire, it is no longer iron; it is fire. Similarly, when we make a form of the Lord—whether of wood or stone or metal or jewels or paint, or even a form within the mind—it is a bona fide, spiritual, transcendental form of the Lord. Not only must one receive the mantra from the bona fide spiritual master like Nārada Muni or his representative in the disciplic succession, but one must chant the mantra. And not only must one chant, but he should also offer whatever foodstuff is available in his part of the world, according to time and convenience.
The method of worship—chanting the mantra and preparing the forms of the Lord—is not stereotyped, nor is it exactly the same everywhere. It is specifically mentioned in this verse that one should take consideration of the time, place and available conveniences. Our Kṛṣṇa consciousness movement is going on throughout the entire world, and we also install Deities in different centers. Sometimes our Indian friends, puffed up with concocted notions, criticize, "This has not been done. That has not been done." But they forget this instruction of Nārada Muni to one of the greatest Vaiṣṇavas, Dhruva Mahārāja. One has to consider the particular time, country and conveniences. What is convenient in India may not be convenient in the Western countries. Those who are not actually in the line of ācāryas, or who personally have no knowledge of how to act in the role of ācārya, unnecessarily criticize the activities of the ISKCON movement in countries outside of India. The fact is that such critics cannot do anything personally to spread Kṛṣṇa consciousness. If someone does go and preach, taking all risks and allowing all considerations for time and place, it might be that there are changes in the manner of worship, but that is not at all faulty according to śāstra. Śrīmad Vīrarāghava Ācārya, an ācārya in the disciplic succession of the Rāmānuja-sampradāya, has remarked in his commentary that caṇḍālas, or conditioned souls who are born in lower than śūdra families, can also be initiated according to circumstances. The formalities may be slightly changed here and there to make them Vaiṣṇavas.
Lord Caitanya Mahāprabhu recommends that His name should be heard in every nook and corner of the world. How is this possible unless one preaches everywhere? The cult of Lord Caitanya Mahāprabhu is bhāgavata-dharma, and He especially recommends kṛṣṇa-kathā, or the cult of Bhagavad-gītā and Śrīmad-Bhāgavatam. He recommends that every Indian, considering this task to be para-upakāra, or welfare activity, take the Lord's message to other residents of the world. "Other residents of the world" does not refer only to those who are exactly like the Indian brāhmaṇas and kṣatriyas, or like the caste brāhmaṇas, who claim to be brāhmaṇas because they were born in the families of brāhmaṇas. The principle that only Indians and Hindus should be brought into the Vaiṣṇava cult is a mistaken idea. There should be propaganda to bring everyone to the Vaiṣṇava cult. The Kṛṣṇa consciousness movement is meant for this purpose. There is no bar to propagating the Kṛṣṇa consciousness movement even among people who are born in caṇḍāla, mleccha or yavana families. Even in India, this point has been enunciated by Śrīla Sanātana Gosvāmī in his book Hari-bhakti-vilāsa, which is smṛti and is the authorized Vedic guide for Vaiṣṇavas in their daily behavior. Sanātana Gosvāmī says that as bell metal can turn to gold when mixed with mercury in a chemical process, so, by the bona fide dīkṣā, or initiation method, anyone can become a Vaiṣṇava. One should take initiation from a bona fide spiritual master coming in the disciplic succession, who is authorized by his predecessor spiritual master. This is called dīkṣā-vidhāna. Lord Kṛṣṇa states in Bhagavad-gītā, vyapāśritya: one should accept a spiritual master. By this process the entire world can be converted to Kṛṣṇa consciousness.