Valmiki Ramayana Ayodhya Kanda Sarga 67 Shloka 33
Original Shlokaयथा दृष्टि श्शरीरस्य नित्यमेव प्रवर्तते। तथा नरेन्द्रो राष्ट्रस्य प्रभवस्सत्यधर्मयोः।।2.67.33।।
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दृष्टिः eye, नित्यमेव perpetually, यथा as, शरीरस्य of the body (for its protection), प्रवर्तते is engaged, तथा similarly, नरेन्द्रः king, राष्ट्रस्य for the country's, सत्यधर्मयोः for truth and ethics, प्रभवः is the source.
The king is the source for protecting the truth and morality of a country like the eye which perpetually watches the welfare of the body.