Who requires a guru? It is not a fashion, that one has to accept anyone as guru. No. A person requires a guru when he is inquisitive, tasmād guruṁ prapadyeta jijñāsuḥ, when he is very much eager to understand the spiritual, śreya uttamam. Uttamam. Ut means transcendental, and tama means darkness. This world is called darkness, ignorance. So one who wants to transcend this position of ignorance and wants to know the transcendental subject, means spiritual subject, brahma-jijñāsā, he requires a guru, not any person, other person.
-Lecture Chaitanya Charitamrit Madhya Chapter 20 Verse 101-104 - Bombay

वासुदेवे भगवति भक्तियोग: प्रयोजित: ।
जनयत्याशु वैराग्यं ज्ञानं च यदहैतुकम् ॥ ७ ॥
By rendering devotional service unto the Personality of Godhead, Śrī Kṛṣṇa, one immediately acquires causeless knowledge and detachment from the world.
-SB 1.2.7