Bhashya
यः कश्चित्, एनम् अश्वमग्निरूपमर्कं च यथोक्तम्, एवं वक्ष्यमाणेन समासेन प्रदर्श्यमानेन विशेषणेन विशिष्टं वेद, स एषोऽश्वमेधं वेद, नान्यः ; तस्मादेवं वेदितव्य इत्यर्थः ।कथम् ? तत्र पशुविषय-
In plain words
Whoever knows this horse—manifested as Agni and Arka in the manner described, and qualified by the specific attributes about to be presented—he alone truly knows the horse-sacrifice, and no other. Therefore, it must be understood precisely in this way. How? Concerning the animal subject—
Close to the Sanskrit
Whosoever knows this horse, having the form of Agni and Arka as stated, qualified by the attribute shown through the compound about to be stated, he alone knows the horse-sacrifice, no other; therefore it is to be known thus, is the meaning. How? There regarding the animal subject-