Kena Upanishad Verse 1.6
The eye sees external forms, but it cannot see the Atman. Instead, it is the Atman that provides the very capacity for vision. This verse redirects the seeker’s attention from the seen to the internal Seeer.
Sanskrit Verse
यच्चक्षुषा न पश्यति येन चक्षूँषि पश्यति ।
तदेव ब्रह्म त्वं विद्धि नेदं यदिदमुपासते ॥ ६ ॥
Transliteration
yaccakṣuṣā na paśyati yena cakṣūm̐ṣi paśyati |
tadeva brahma tvaṃ viddhi nedaṃ yadidamupāsate || 6 ||
Translation
What cannot be seen by the eye, but by which the eyes are able to see. That alone know thou to be the Brahman; not this which (people) here worship.

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