Bhashya
धेन यजते य उ चैनमेवं वेद' इति विकल्पश्रुतेः ।विद्याप्रकरणे चाम्नानात्, कर्मान्तरे च संपादनदर्शनात्, विज्ञानात्तत्फलप्राप्तिरस्तीत्यवगम्यते ।सर्वेषां च कर्मणां परं कर्माश्वमेधः, समष्टिव्यष्टिप्राप्तिफलत्वात् ।तस्य चेह ब्रह्मविद्याप्रारम्भे आम्नानं सर्वकर्मणां संसारविषयत्वप्रदर्शनार्थम् ।तथा च दर्शयिष्यति फलमशनायामृत्युभावम् ।न नित्यानां संसारविषयफलत्वमिति चेत्, न; सर्वकर्मपलोपसंहारश्रुतेः ।सर्वं हि पत्नीसंबद्धं कर्म ; 'जाया मे स्यादेतावान्वै कामः' इति निसर्गत एव सर्वकर्मणां काम्यत्वं दर्शयित्वा, पुत्रकर्मापरविद्यानां च 'अयं लोकः पितृलोको देवलोकः' इति फलं दर्शयित्वा, त्र्यन्नात्मकतां चान्ते उपसंहरिष्यति 'त्रयं वा इदं नाम रूपं कर्म' इति--सर्वकर्मणां फलं व्याकृतं संसार एवेति ।इदमेव त्रयं प्रागुत्पत्तेस्तर्ह्यव्याकृतमासीत् ।तदेव पुनः सर्वप्राणिकर्मवशाद्व्याक्रियते बीजादिव वृक्षः ।सोऽयं व्याकृताव्याकृतरूपः संसारोऽविद्याविषयः क्रियाकारकफलात्मकतयात्मरूपत्वेनाध्यारोपितोऽविद्ययैव मूर्तामूर्ततद्वासनात्मकः ।अतो विलक्षणोऽनामरूपकर्मात्मकोऽद्वयो नित्यशुद्धबुद्धमुक्तस्वभावोऽपि क्रियाकारकफलभेदादिविपर्ययेणावभासते ।अतोऽस्मात्क्रियाकारकभेदस्वरूपात् 'एतावदिदम्' इति साध्य-
In plain words
Because scripture notes 'He sacrifices with a cow if one knows thus', and because such rituals are placed within the context of knowledge and their results are observed, we understand that results follow upon understanding. The horse sacrifice stands supreme among rituals because its fruits encompass both universal and individual attainment. Its placement at the very outset of the teaching on Brahman serves to demonstrate that all ritual action belongs entirely to the realm of saṃsāra. Scripture itself will reveal hunger and death as the ultimate fruit of such action. Should one object that permanent daily obligations do not result in saṃsāra, we reply that they do, because scripture concludes that every action bears fruit. All ritual is tied to a domestic partner—as the text declares: 'May my wife be mine, for this is the extent of desire'—revealing that ritual action is naturally driven by desire. Having shown that the fruits of progeny, ritual, and lower knowledge are respectively this world, the world of the ancestors, and the world of the gods, scripture concludes that this entire triad consists merely of name, form, and action, proving that the fruit of all ritual is nothing other than the phenomenal saṃsāra. Before creation, this same triad existed in an unmanifest state. It is projected once more by the momentum of the karma of all living beings, just as a tree emerges from a seed. This whole network of manifest and unmanifest existence—the domain of ignorance made of action, instruments, and results—is superimposed upon the pure Self purely through nescience, laden with the impressions of the gross and subtle. Yet the non-dual Self is entirely distinct from all this: devoid of name, form, and action, intrinsically pure, conscious, free, and eternal. It merely appears distorted through the lens of agency, action, and fruit. Therefore, departing from this realm of fragmented action...
Close to the Sanskrit
Since scripture states 'He sacrifices with a cow if one knows thus', through option and inclusion in knowledge sections and observation of results, it is known that the result of knowledge is attained. The horse sacrifice is the supreme among all actions because it yields collective and individual attainments. Its mention at the beginning of the knowledge of Brahman is to show that all actions belong to saṃsāra. Scripture will show hunger and death as its fruit. If it is objected that permanent duties do not have saṃsāra as their fruit, we say no, because scripture concludes that all actions bear fruit. All ritual action is connected with a wife, as shown by 'May my wife be mine, this much indeed is desire', showing that all actions are naturally motivated by desire. Having shown the fruit of progeny, rites, and lower knowledge as this world, the world of fathers, and the world of gods, scripture concludes at the end that this triad is name, form, and action—showing that the fruit of all actions is simply the manifest saṃsāra. This very triad existed as unmanifest before creation. That same unmanifest state is manifested again by the force of the karma of all beings, like a tree from a seed. This saṃsāra of manifest and unmanifest forms, which is the domain of ignorance consisting of action, agency, and fruit, is falsely superimposed on the Self solely through ignorance, possessing the subtle impressions of the formed and unformed. Therefore, the non-dual Self, which is distinct from this, devoid of name, form, and action, and whose nature is eternal purity, awareness, and freedom, appears as if subject to the reversal of distinctions such as action, agent, and fruit. Hence, from this true nature of action and agency...