Bhagavad Gita: Chapter 13, Verse 34

यथा प्रकाशयत्येक: कृत्स्नं लोकमिमं रवि: |
क्षेत्रं क्षेत्री तथा कृत्स्नं प्रकाशयति भारत || 34||

yathā prakāśhayaty ekaḥ kṛitsnaṁ lokam imaṁ raviḥ
kṣhetraṁ kṣhetrī tathā kṛitsnaṁ prakāśhayati bhārata

yathāas; prakāśhayatiillumines; ekaḥone; kṛitsnamentire; lokamsolar system; imamthis; raviḥsun; kṣhetramthe body; kṣhetrīthe soul; tathāso; kṛitsnamentire; prakāśhayatiillumine; bhārataArjun, the son of Bharat

yatha prakashayaty ekah kritsnam lokam imam ravih
kshetram kshetri tatha kritsnam prakashayati bharata


BG 13.34: Just as one sun illumines the entire solar system, so does the individual soul illumine the entire body (with consciousness).


Although the soul energizes the entire body in which it is present with consciousness, yet by itself, it is exceedingly small.  eṣho ’ṇurātmā  (Muṇḍakopaniṣhad 3.1.9) “The soul is very tiny in size.”  The Śhwetāśhvatar Upaniṣhad states:

bālāgraśhatabhāgasya śhatadhā kalpitasya cha

bhāgo jīvaḥ sa vijñeyaḥ sa chānantyāya kalpate   (5.9)

“If we divide the tip of a hair into a hundred parts, and then divide each part into further hundred parts, we will get the size of the soul.  These souls are innumerable in number.”  This is a manner of expressing the minuteness of the soul. 

How can such an infinitesimal soul energize the body, which is huge in comparison?   Shree Krishna explains this with the analogy of the sun.  Although situated in one place, the sun illumines the entire solar system with its light.  Likewise, the Vedānt Darśhan states:

guṇādvā lokavat   (2.3.25)  

“The soul, although seated in the heart spreads its consciousness throughout the field of the body.”