Śrīmad-Bhāgavatam · Text 11.3.21
Who is speaking and story frame
तस्माद् गुरुं प्रपद्येत जिज्ञासु: श्रेय उत्तमम् ।
शाब्दे परे च निष्णातं ब्रह्मण्युपशमाश्रयम् ॥ २१ ॥
tasmād guruṁ prapadyeta
jijñāsuḥ śreya uttamam
śābde pare ca niṣṇātaṁ
brahmaṇy upaśamāśrayam
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.
Read the purport on Vedabase.ioFrom Canto 10, chapter 14 onward, the translation and purports were completed by Śrīla Prabhupāda's disciples after his departure, and published by the Bhaktivedanta Book Trust.