Kaṭha Upaniṣad · 2.2.11

सूर्यो यथा सर्वलोकस्य चक्शुर्न लिप्यते चाक्शुषैर्बाह्यदोषैः । एकस्तथा सर्वभूतान्तरात्मा न लिप्यते लोकदुःखेन बाह्यः ॥ ११ ॥

sūryo yathā sarvalokasya cakśurna lipyate cākśuṣairbāhyadoṣaiḥ | ekastathā sarvabhūtāntarātmā na lipyate lokaduḥkhena bāhyaḥ || 11 ||

As the sun, the eye of the entire world, is not contaminated by the external impurities seen by the eyes, so the one Ātman, the inner Self of all beings, is not contaminated by the suffering of the world, for it is beyond it.

The metaphor of sūrya (the sun) reveals a profound truth about the nature of Ātman: although it illuminates and makes all experience possible, it remains immaculate from the content of that experience. The sun that reveals impure objects is not defiled by them; likewise, the Ātman that witnesses suffering does not suffer.

The word lipyate (is contaminated, adheres) comes from the root lip implying sticky contact. The Ātman is like space: things happen within it, but they never stain it. Suffering—the duḥkha of the world—appears in the field of mind and senses, not in the essential nature of the witness.

This teaching is fundamental to the practice of vairāgya (dispassion, non-attachment). It does not mean denying the suffering of others, but understanding that our true being has never been touched by it. The yogi who realizes this truth can act with compassion from a place of unshakeable peace, without being dragged by the turbulences of saṃsāra.