Kaṭha Upaniṣad 219

219

agnir yathaiko bhuvanaṃ praviṣṭo rūpaṃ rūpaṃ pratirūpo babhūva /
ekas tathā sarvabhūtāntarātmā rūpaṃ rūpaṃ pratirūpo bahiś ca ///2,2.9 //

9. As fire, though one, having entered the world, takes a separate form in respect of every form, so does the internal atman of all living things assume a form for every form and is outside all forms.