One verse

Srimad Bhagavatam 11.3.21

11.3.21

तस्माद् गुरुं प्रपद्येत जिज्ञासु: श्रेय उत्तमम् । शाब्दे परे च निष्णातं ब्रह्मण्युपशमाश्रयम् ॥ २१ ॥

tasmād guruṁ prapadyeta jijñāsuḥ śreya uttamam śābde pare ca niṣṇātaṁ brahmaṇy upaśamāśrayam

tasmāt
therefore
gurum
a spiritual master
prapadyeta
one should take shelter of
jijñāsuḥ
being inquisitive
śreyaḥ uttamam
about the highest good
śābde
in the Vedas
pare
in the Supreme
ca
and
niṣṇātam
perfectly knowledgeable
brahmaṇi
(in these two aspects) of the Absolute Truth
upaśama-āśrayam
fixed in detachment from material affairs

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.