The mahā-bhāgavata is one who decorates his body with tilaka and whose name indicates him to be a servant of Kṛṣṇa by the word dāsa. He is also initiated by a bona fide spiritual master and is expert in worshiping the Deity, chanting mantras correctly, performing sacrifices, offering prayers to the Lord and performing saṅkīrtana. He knows how to serve the Supreme Personality of Godhead and how to respect a Vaiṣṇava. When one has attained the topmost position of mahā-bhāgavata, he is to be accepted as a guru and worshiped exactly like Hari, the Personality of Godhead. Only such a person is eligible to occupy the post of a guru. However, if one is highly qualified but is not a Vaiṣṇava, he cannot be accepted as a guru. One cannot be a brāhmaṇa unless one is a Vaiṣṇava. If one is a Vaiṣṇava, he is already a brāhmaṇa. If a guru is completely qualified as a Vaiṣṇava, he must be accepted as a brāhmaṇa even if he is not born in a brāhmaṇa family. The caste system method of distinguishing a brāhmaṇa by birth is not acceptable when applied to a bona fide spiritual master. A spiritual master is a qualified brāhmaṇa and ācārya. If one is not a qualified brāhmaṇa, he is not expert in studying the Vedic literatures. Nānā-śāstra-vicāraṇaika-nipuṇau. Every Vaiṣṇava is a spiritual master, and a spiritual master is automatically expert in brahminical behavior. He also understands the Vedic śāstras.
Similarly, a disciple’s qualifications must be observed by the spiritual master before he is accepted as a disciple. In our Kṛṣṇa consciousness movement, the requirement is that one must be prepared to give up the four pillars of sinful life—illicit sex, meat-eating, intoxication and gambling. In Western countries especially, we first observe whether a potential disciple is prepared to follow the regulative principles. Then he is given the name of a Vaiṣṇava servant and initiated to chant the Hare Kṛṣṇa mahā-mantra, at least sixteen rounds daily. In this way the disciple renders devotional service under the guidance of the spiritual master or his representative for at least six months to a year. He is then recommended for a second initiation, during which a sacred thread is offered and the disciple is accepted as a bona fide brāhmaṇa. Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura introduced the system of giving the sacred thread to a bona fide Vaiṣṇava, and we are following in his footsteps.