सोऽकामयत मेध्यं म इदं स्यादात्मन्व्यनेन स्यामिति ।ततोऽश्वः समभवत् ।यदश्वत्तन्मेध्यमभूदिति तदेवाश्वमेधस्याश्वमेधत्वम् ।एष ह वा अश्वमेधं वेद य एनमेवं वेद ।तमनवरुध्यैवामन्यत ।तं संवत्सरस्य परस्तादात्मन आलभत ।पशून् देवताभ्यः प्रत्यौहत् ।तस्मात्सर्वदेवत्यं प्रोक्षितं प्राजापत्यमालभन्ते ।एष वा अश्वमेधो य एष तपति ।तस्य संवत्सर आत्मा ।अयमग्निरर्कः ।तस्येमे लोका आत्मानः ।तावेतावर्काश्वमेधौ ।सो पुनरेकैव देवता भवति मृत्युरेव ।अप पुनर्मृत्युं जयति ।नैनं मृत्युराप्नोति ।मृत्युरस्यात्मा भवति ।सर्वमायुरेति ।एतासां देवतानामेको भवति ॥बृह. १,२.७ ॥
In plain words
He desired, "Let this body of mine be fit for sacrifice, and let me have a self through it." Then it became a horse; and because it swelled it became fit for sacrifice — that is the horse-sacrifice-hood of the horse sacrifice. He indeed knows the horse sacrifice who knows it thus. He let it go free and thought upon it; and after a year he offered it up to himself. He handed over the other animals to the deities; and therefore men offer up to Prajāpati the victim consecrated to all the gods. This sun that gives heat is the horse sacrifice, and the year is its body. This fire is the arka, and these worlds are its bodies. So there are these two, the arka and the horse sacrifice; and again they are one deity, Death itself. He conquers repeated death; death does not reach him; death becomes his self; he reaches his full span of life and becomes one of these deities.
The commentators
Bṛhadāraṇyakopaniṣadbhāṣyam
स तस्मिन्नेव शरीरे गतमनः सन्किमकरोदिति, उच्यते— सोऽकामयत । कथम् ? मेध्यं मेधार्हं यज्ञियं मे मम इदं शरीरम् स्यात् ; किंच आत्मन्वी आत्मवांश्च अनेन शरीरेण शरीरवान् स्यामिति— प्रविवेश । यस्मात् तच्छरीरं तद्वियोगाद्रतयशोवीर्यं सत् अश्वत् अश्वयत्, ततः तस्मात् अश्वः समभवत् ; ततोऽश्वनामा प्रजापतिरेव साक्षादिति स्तूयते ; यस्माच्च पुनस्तत्प्रवेशात् गतयशोवीर्यत्वाद्मेध्यं सत् मेध्यमभूत्, तदेव तस्मादेव अश्वमेधस्य अश्वमेधनाम्नः क्रतोः अश्वमेधत्वम् अश्वमेधनामलाभः ; क्रियाकारकफलात्मको हि क्रतुः ; स च प्रजापतिरेवेति स्तूयते ।
क्रतुनिर्वर्तकस्याश्वस्य प्रजापतित्वमुक्तम्—'उषा वा अश्वस्य मेध्यस्य' इत्यादिना । तस्यैवाश्वस्य मेध्यस्य प्रजापतिस्वरूपस्य अग्नेश्च यथोक्तस्य क्रतुफलात्मरूपतया समस्योपासनं विधातव्यमित्यारभ्यते । पूर्वत्र क्रियापदस्य विधायकस्याश्रुतत्वात्, क्रियापदापेक्षत्वाच्च प्रकरणस्य, अयमर्थोऽवगम्यते ।
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
He entered that very body, his mind fully absorbed, and asked: What is to be done? He desired: May this body of mine become pure and fit for sacrifice, and may I be fully embodied within it. With this thought, he entered. Because that body lacked glory and vitality in his absence and cried out, the horse was born from it; and thus it is directly glorified as Prajāpati, bearing the name of the horse. And because that very body, upon his entry, regained its sacred fitness, that ritual acquired its name and nature as the great horse-sacrifice—for every sacrifice consists of action, means, and fruit, and that sacrifice is indeed none other than Prajāpati.
The previous section identified the sacrificial horse with the cosmic creator, Prajāpati, beginning with the words, 'Dawn, indeed, is the head of the sacrificial horse.' Now, this next section begins in order to prescribe a unified meditation on that very horse (as Prajāpati) and the sacrificial fire, viewing them both as the ultimate fruit of the ritual. We know this is the intended meaning because no commanding verb was explicitly stated in the opening passage, and the context itself demands such a verb to complete its sense.
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
He residing in that very body having entered with mind, what did he do, is said: He desired. How? May this body of mine be fit for sacrifice, worthy of oblation, sacrificial, and may I, endowed with self and possessing a self, be embodied with this body, thus—he entered. Because that body, being stripped of glory and vigor through separation from him, lamented, therefore from that the horse came into being; thence he is praised directly as Prajāpati named horse; and because that very thing, through that entry, having lost its glory and vigor, became fit for sacrifice, therefore alone the horse-sacrifice's being an horse-sacrifice and the attainment of the name horse-sacrifice belong to that sacrifice of the nature of action, instrument, and fruit; and that is praised as Prajāpati indeed.
The identity with Prajāpati of the horse that accomplishes the sacrifice has been stated by [the passage] beginning with 'Dawn, indeed, [is the head] of the sacrificial horse'. The collective meditation of that very sacrificial horse, whose nature is Prajāpati, and of the fire as described, as being of the nature of the fruit of the sacrifice, is to be prescribed—thus [this section] is begun. Because in the earlier part an enjoining verb was not heard, and because the context requires a verb, this meaning is understood.
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-