Srimad Bhagavatam

References to text SB 11.3.21
SB 11.3.21: Therefore any person who seriously desires real happiness must seek a bona fide spiritual master and take shelter of him by initiation. The qualification of the bona fide guru is that he has realized the conclusions of the scriptures by deliberation and is able to convince others of these conclusions. Such great personalities, who have taken shelter of the Supreme Godhead, leaving aside all material considerations, should be understood to be bona fide spiritual masters.

Text â„–
“Your book should describe the characteristics of the bona fide guru and the bona fide disciple. Then, before accepting a spiritual master, one can be assured of the spiritual master’s position. Similarly, the spiritual master can also be assured of the disciple’s position. The Supreme Personality of Godhead, Kṛṣṇa, should be described as the worshipable object, and you should describe the bÄ«ja-mantra for the worship of Kṛṣṇa, as well as that for RÄma and for other expansions of the Supreme Personality of Godhead.
The Sixty-One Explanations of the Atmarama Verse
CC 2.24.330