Srila Bhaktisiddhanta Sarasvati Thakur Prabhupada
“The mahā-bhāgavata is the true guru. Only someone who has achieved the status of mahā-bhāgavata can take the role of spiritual master. One can act as guru when he himself sees the guru everywhere, for such a person can transform another insignificant individual into one capable of imparting spiritual instruction himself. He can turn a non-devotee into a devotee. Evidently, if one is not himself a devotee he cannot make anyone else into a devotee. Thus, the meaning of being guru is being a devotee. All of one’s senses must be engaged in the service of the Lord. If one cannot become fixed in the service of the guru, he has no right to act as guru.
“The mahā-bhāgavata is more humble than the grass in the street. He thinks he is the most insignificant person in the world. He does not think, ‘I have played the role of servant long enough; it’s no fun any more. I need to be guru now.’
“The guru serves as spiritual master, but does not identify himself with that role.”