MUṆḌAKA UPANISHAD · 1.2.12

परीक्ष्य लोकान् कर्मचितान् ब्राह्मणो
निर्वेदमायान्नास्त्यकृतः कृतेन ।
तद्विज्ञानार्थं स गुरुमेवाभिगच्छेत्
समित्पाणिः श्रोत्रियं ब्रह्मनिष्ठम् ॥ १२॥

parīkṣya lokān karmacitān brāhmaṇo
nirvedamāyānnāstyakṛtaḥ kṛtena ।
tadvijñānārthaṃ sa gurumevābhigacchet
samitpāṇiḥ śrotriyaṃ brahmaniṣṭham ॥ 12॥

The seeker of the Brahman, having put to the test the worlds piled up by works, arrives at world-distaste, for not by work done is reached He who is Uncreated. For the knowledge of That, let him approach, fuel in hand, a Guru, one who is learned in the Veda and is devoted to contemplation of the Brahman.

Sri Aurobindo · CWSA 18, p. 135