Verse 3.18.5

चक्षुरेव ब्रह्मणश्चतुर्थः पादः स आदित्येन ज्योतिषा भाति च तपति च भाति च तपति च कीर्त्या यशसा ब्रह्मवर्चसेन य एवं वेद ॥ ३.१८.५ ॥

cakṣureva brahmaṇaścaturthaḥ pādaḥ sa ādityena jyotiṣā bhāti ca tapati ca bhāti ca tapati ca kīrtyā yaśasā brahmavarcasena ya evaṃ veda || 3.18.5 ||

5. The organ of vision is one of the four feet of Brahman [as the mind]. It shines by the light of the sun and also radiates heat. He who knows this shines and radiates warmth with his good work, with his fame, and with the radiance he acquires from leading a scholarly and disciplined life.

Word-for-word explanation:

Cakṣuḥ eva brahmaṇaḥ caturthaḥ pādaḥ, the organ of vision is the fourth foot of [manomaya] Brahman; ādityena jyotiṣā, by the light it gets from the sun [its presiding deity]; saḥ bhāti ca tapati ca, it shines and gives heat; yaḥ evam veda, he who knows thus; bhāti ca tapati ca, shines and radiates warmth; kīrtyā, through good work; yaśasā, through fame; brahmavarcasena, through the radiance that comes from a scholarly and disciplined life.

Commentary:

The eyes can distinguish colours because of the light they get from the sun. Just as cows can feel their way with their feet, similarly, human beings can recognize things through their eyes.

When a person knows how the eyes serve as feet, he acquires fame, glory, and the brightness of Brahman, for he can then make good use of his eyes. He can read and learn the best things possible, things that transform him into a realized soul.