Katha Upanishad Verse 2.1.1

Yama explains that the senses are naturally oriented toward the external world, which distracts humanity from the inner Self. Only the “Dhira” (steady and wise seeker), driven by a desire for immortality, exercises the discipline to turn their vision inward to discover the Pratyagatman (the Inner Self). Only a wise person (Dhira), seeking immortality, turns their vision inward.

Sanskrit Verse

पराञ्चि खानि व्यतृणत्स्वयम्भूस्तस्मात्पराङ्पश्यति नान्तरात्मन् ।
कश्चिद्धीरः प्रत्यगात्मानमैक्षदावृत्तचक्शुरमृतत्वमिच्छन् ॥ १ ॥

Transliteration

parāñci khāni vyatṛṇatsvayambhūstasmātparāṅpaśyati nāntarātman |
kaściddhīraḥ pratyagātmānamaikṣadāvṛttacakśuramṛtatvamicchan || 1 ||

Translation

The self-existent created the senses out-going: therefore, one sees outside and not the atman within. Some intelligent man, with his senses turned away, (from their object), desirous of immortality, sees the atman within.