MUṆḌAKA UPANISHAD · 3.2.4

नायमात्मा बलहीनेन लभ्यो
न च प्रमादात्तपसो वाप्यलिङ्गात् ।
एतैरुपायैर्यतते यस्तु विद्वांस्तस्यैष आत्मा विशते ब्रह्मधाम ॥ ४॥

nāyamātmā balahīnena labhyo
na ca pramādāttapaso vāpyaliṅgāt ।
etairupāyairyatate yastu vidvāṃstasyaiṣa ātmā viśate brahmadhāma ॥ 4॥

This Self cannot be won by any who is without strength, nor with error in the seeking, nor by an askesis without the true mark: but when a man of knowledge strives by these means his self enters into Brahman, his abiding place.

Sri Aurobindo · CWSA 18, p. 145