This phrase was only spoken once, by Srila Prabhupada in a lecture on Bhagavad-gita 16.8, Tokyo Japan, on January 28, 1975:
Budhah. Budha means one who has understood thoroughly. So therefore, he can become… One who has understood thoroughly Krishna as the supreme controller, he is guru. He is guru. Otherwise, one cannot be guru. Sri Caitanya-caritamrita-Madhya-lila 8.128,
“It does not matter whether a person is a Vipra (learned scholar in Vedic wisdom) or is born in a lower family, or is in the renounced order of life—if he is a master in the science of Krishna; he is the perfect and bona fide spiritual master”
Who can (be) guru? Guru is not artificial thing, “Guru Maharaja”, “this “Maharaja…,” no. One who has firmly understood that Krishna is the original cause of everything, He is the Supreme Person; nobody can remove him from that firm convictional position, then he is guru. Otherwise, he is not guru. Guru is not so easy thing. Bhagavad-gita As It Is 10.8,
“I am the source of all spiritual and material worlds. Everything emanates from Me. The wise who perfectly know this engage in My devotional service and worship Me with all their hearts.”
One who has understood Krishna as the Supreme Personality of Godhead, the supreme controller, the supreme maintainer, the Supreme Person, everything, only one, Bhagavad-gita As It Is 6.19,
“A lamp in a windless place does not waver, so the transcendentalist, whose mind is controlled, remains always steady in his meditation on the transcendent self.”
That is guru. But otherwir eyes.
One who has understood Krishna as the supreme controller, the Supreme Person, the supreme maintainer, and everything, the supreme, ultimate, then he can become guru. Otherwise, do not try to become guru.
This is the Caitanya Mahaprabhu’s formula. Therefore, first of all try to understand Krishna. You will understand in such a way that you can refute all others’ argument, all others’ opposition. There are so many opposing elements. Then you are guru. Otherwise, you cannot become a guru. Guru is not so teeny thing or trifle thing that everyone becomes Guru Maharaja, no. That is not guru. Bhagavad-gita As It Is 7.19,
‘After many births and deaths, he who is actually in knowledge surrenders unto Me, knowing Me to be the cause of all causes and all that is. Such a great soul is very rare’.’’
In this reference, Srila Prabhupada recited two scriptural references. One from Bhagavad-gita As It Is, and the other one from Sri Caitanya-caritamrita. This is very special, because Srila Prabhupada’s instructions, on “guru”, are confirmed by Krishna in the Bhagavad-gita As It Is, and Lord Caitanya in the Sri Caitanya-caritamrita. In other words, Srila Prabhupada was simply repeating the instruction of Lord Krishna, and Lord Caitanya.
When one understands Krishna in such a way that he can refute all other arguments, all opposition, one can be guru. Becoming guru does not necessitate esoteric qualifications. One simply has to be a professor of the science of Krishna, a transparent via medium for the parampara. That is all. Moreover, the prospective disciple must know enough of the science, so that he or she can ascertain whether or not the guru is qualified in the science. There is no necessity to resort to the ritvik rhetoric, to understand guru-tattva without the support of sastra. As Prabhupada says, “It is not blind. It is not blind.” No. Sastra is ou