In plain words
As the one sun illumines this entire world, so the kṣetrin illumines the whole kṣetra, Bharata.
Word for word
As the one sun illumines this entire world, so the kṣetrin illumines the entire kṣetra, O Bhārata.
यथा प्रकाशयत्येकः कृत्स्नं लोकमिमं रविःक्षेत्रं क्षेत्री तथा कृत्स्नं प्रकाशयति भारत
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam
किञ्च —
यथा प्रकाशयति अवभासयति एकः कृत्स्नं लोकम् इमं रविः सविता आदित्यः, तथा तद्वत् महाभूतादि धृत्यन्तं क्षेत्रम् एकः सन् प्रकाशयति । कः ? क्षेत्री परमात्मा इत्यर्थः । रविदृष्टान्तः अत्र आत्मनः उभयार्थोऽपि भवति — रविवत् सर्वक्षेत्रेषु एक एव आत्मा, अलेपकश्च इति ॥ ३३ ॥
In plain words
And there is more —
Think of the sun, the one great light-giver, illuminating this entire world all by itself. In exactly the same way, one single source illuminates the whole field, from the coarse elements all the way to the subtlest faculty of steadiness. And who is that source? It's the possessor of the field, the Supreme Self. This sun-comparison actually does double work here: just like the sun, the Self is one and the same in every single body, and just like the sun, nothing it touches ever stains it.
Close to the Sanskrit
And what more —
Just as the sun, the begetter, the sun-orb, being one, illuminates, lights up, this entire world — so, in that same way, being one, it illuminates the field extending from the great elements to steadiness. Who? The possessor of the field, the Supreme Self: that is the meaning. This sun-example here serves a double purpose regarding the Self: like the sun, the Self is one alone in all fields, and it is untainted — thus.