Katha Upanishad Verse 2.2.10

Like wind, which is a single element but assumes the shape of whatever it fills, the internal Self of all beings remains essentially one while manifesting in multiple forms, remaining untainted by them.

Sanskrit Verse

वायुर्यथैको भुवनं प्रविष्टो रूपं रूपं प्रतिरूपो बभूव ।
एकस्तथा सर्वभूतान्तरात्मा रूपं रूपं प्रतिरूपो बहिश्च ॥ १० ॥

Transliteration

vāyuryathaiko bhuvanaṃ praviṣṭo rūpaṃ rūpaṃ pratirūpo babhūva |
ekastathā sarvebhūtāntarātmā rūpaṃ rūpaṃ pratirūpo bahiśca || 10 ||

Translation

As wind, though one, having entered the world, assumes forms responsive to every form, so the internal atman of all living things, though one, assumes forms responsive to every form and is outside them all.