mahā-kula-prasūto 'pi sarva-yajñeṣu dīkṣitaḥ sahasra-śākhādhyāyī ca na guruḥ syād avaiṣṇavaḥ

maha-kula-prasuto 'pi
sarva-yajnesu diksitah
sahasra-sakhadhyayi ca
na guruh syad avaisnavah
The guru must be situated on the topmost platform of devotional service. There are three classes of devotees, and the guru must be accepted from the topmost class. The first-class devotee is the spiritual master for all kinds of people. It is said: gurur nrnam. The word nrnam means "of all human beings." The guru is not limited to a particular group. It is stated in the Upadesamrta [1] of Rupa Gosvami that a guru is a gosvami, a controller of the senses and the mind. Such a guru can accept disciples from all over the world. Prthivim sa sisyat. This is the test of the guru.
In India there are many so-called gurus, and they are limited to a certain district or a province. They do not even travel about India, yet they declare themselves to be jagad-guru, gurus of the whole world. Such cheating gurus should not be accepted. Anyone can see how the bona fide spiritual master accepts disciples from all over the world. The guru is a qualified brahmana; therefore he knows Brahman and Parabrahman. He thus devotes his life for the service of Parabrahman. The bona fide spiritual master who accepts disciples from all over the world is also worshiped all over the world because of his qualities. Lokanam asau pujyo yatha harih: the people of the world worship him just as they worship the Supreme Personality of Godhead. All these honors are offered to him because he strictly follows the brahminical principles and teaches these principles to his disciples. Such a person is called an acarya because he knows the principles of devotional service, he behaves in that way himself, and he teaches his disciples to follow in his footsteps. Thus he is an acarya or jagad-guru. Even though a person is born in a brahminical family and is very expert in performing sacrifices, he cannot be accepted as a guru if he is not a strict Vaisnava. A guru is a brahmana by qualification, and he can turn others into brahmanas according to the sastric principles and brahminical qualifications. Brahmanism is not a question of heredity. In Srimad-Bhagavatam (7.32.11) Sri Narada Muni tells Maharaja Yudhisthira what a brahmana is. He states that if brahminical qualifications are observed in ksatriyas, vaisyas or even sudras, one should accept them as brahmanas. In this regard, Srila Sridhara Svami has commented: samadibhir eva brahmanadi-vyavaharo mukhyah, na jati-matradity aha-yasyeti. yad yadi anyatra varnantare 'pi drsyeta, tad-varnantaram tenaiva laksana-nimittenaiva varnena vinirdiset, na tu jati-nimittenety arthah.
There is a similar statement made by Nilakantha, the commentator on Mahabharata: