अथ ये यज्ञेन दानेन तपसा लोकाञ्जयन्ति ते धूममभिसंभवन्ति ।धूमाद्रात्रिम् ।रात्रेरपक्षीयमाणपक्षम् ।अपक्षीयमाणपक्षाद्यान् षण्मासान् दक्षिणादित्य एति ।मासेभ्यः पितृलोकम् ।पितृलोकाच्चन्द्रम् ।ते चन्द्रं प्राप्यान्नं भवन्ति ।तांस्तत्र देवा यथा सोमं राजानमाप्यायस्वापक्षीयस्वेत्येवमेनांस्तत्र भक्षयन्ति ।तेषां यदा तत्पर्यवैत्यथेममेवाकाशमभिनिष्पद्यन्ते ।आकाशाद्वायुम् ।वायोर्वृष्टिम् ।वृष्टेः पृथिवीम् ।ते पृथिवीं प्राप्यान्नं भवन्ति ।ते पुनः पुरुषाग्नौ हूयन्ते ततो योषाग्नौ जायन्ते ।लोकान् प्रत्युथायिनस्त एवमेवानुपरिवर्तन्ते ।अथ य एतौ पन्थानौ न विदुस्ते कीटाः पतङ्गा यदिदं दन्दशूकम् ॥६,२.१६ ॥
In plain words
But those who win their worlds by sacrifice, by giving and by austerity go on to the smoke, from the smoke to the night, from the night to the dark fortnight, from the dark fortnight to the six months in which the sun moves south, from those months to the world of the fathers, from the world of the fathers to the moon. Reaching the moon they become food; and there the gods eat them, as men say to King Soma, "Wax full, wane." And when that is spent, they come forth into this space; from space to the wind, from the wind to rain, from rain to the earth. Reaching the earth they become food. They are offered again in the fire of a man, and thence are born in the fire of a woman. Rising up again to the worlds, they go round in the same way. But those who know neither of these two paths become worms and insects and whatever there is here that bites."
The commentators
Bṛhadāraṇyakopaniṣadbhāṣyam· Leaf 10.112· bhāṣya
पि देवता एव धूमादिशब्दवाच्याः, धूमदेवतां प्रतिपद्यन्त इत्यर्थः; आतिवाहिकत्वं च देवतानां तद्वदेव। धूमान् रात्रिं रात्रिदेवताम्, ततः अपक्षीयमाणपक्षम् अपक्षीयमाणपक्ष- देवताम्, ततो यान्षण्मासान् दक्षिणां दिशमादित्य एति तान् मासदेवताविशेषान् प्रतिपद्यन्ते। मासेभ्यः पितृलोकम्, पितृ- लोकाच्चन्द्रम्। ते चन्द्रं प्राप्य अन्नं भवन्ति; तान् तत्रान्नभू- तान्, यथा सोमं राजानमिह यज्ञे ऋत्विजः आप्यायस्व अ- पक्षीयस्वेति भक्षयन्ति, एवम् एनान् चन्द्रं प्राप्तान् कर्मिणः भृत्यानिव स्वामिनः भक्षयन्ति उपभुञ्जते देवाः; 'आप्याय- स्वापक्षीयस्व' इति न मन्त्रः; किं तर्हि आप्याय्य आप्याय्य चमसस्थम्, भक्षणेन अपक्षयं च कृत्वा, पुनः पुनर्भक्षयन्ती- त्यर्थः; एवं देवा अपि सोमलोके लब्धशरीरान् कर्मिणः उप- करणभूतान् पुनः पुनः विश्रामयन्तः कर्मानुरूपं फलं प्रयच्छ- न्तः-तद्धि तेषामाप्यायनं सोमस्य आप्यायनमिव उपभुञ्जते उपकरणभूतान् देवाः। तेषां कर्मिणाम् यदा यस्मिन्काले, तत् यज्ञदानादिलक्षणं सोमलोकप्रापकं कर्म, पर्यवैति परि- गच्छति परिक्षीयत इत्यर्थः, अथ तदा इममेव प्रसिद्धमा- काशमभिनिष्पद्यन्ते; यास्ताः श्रद्धाशब्दवाच्या द्युलोकाग्नौ हुता आपः सोमाकारपरिणताः, याभिः सोमलोके कर्मिणामु- पभोगाय शरीरमारब्धम् अम्मयम्, ताः कर्मक्षयान् हि- मपिण्ड इवातपसंपर्कात् प्रविलीयन्ते; प्रविलीनाः सू- क्ष्मा आकाशभूता इव भवन्ति; तदिदमुच्यते- 'इममे- वाकाशमभिनिष्पद्यन्ते' इति । ते पुनरपि कर्मिणः त- च्छरीराः सन्तः पुरोवातादिना इतश्च अमुतश्च नीयन्ते अन्तरिक्षगाः; तदाह- आकाशाद्वायुमिति । वायोर्वृष्टिं प्रतिपद्यन्ते; तदुक्तम्- पर्जन्याग्नौ सोमं राजानं जुह्वती- ति । ततो वृष्टिभूता इमां पृथिवीं पतन्ति । ते पृथिवीं प्राप्य व्रीहियवादि अन्नं भवन्ति; तदुक्तम्- अस्मिँल्लोकेऽग्नौ वृष्टिं जुह्वति तस्या आहुत्या अन्नं संभवतीति । ते पुनः पुरु- षाग्नौ हूयन्ते अन्नभूता रेतःसिचि; ततो रेतोभूता योषान्नौ हूयन्ते; ततो जायन्ते; लोकं प्रत्युत्थायिनः ते लोकं प्रत्यु- त्तिष्ठन्तः अग्निहोत्रादिकर्म अनुतिष्ठन्ति । ततो धूमादिना पुनः पुनः सोमलोकम्, पुनरिमं लोकमिति- ते एवं कर्मिणः अनुपरिवर्तन्ते घटीयन्त्रवत् चक्रीभूता बंभ्रमतीत्य- र्थः, उत्तरमार्गाय सद्योमुक्तये वा यावद्ब्रह्म न विदुः; 'इति नु कामयमानः संसरति' इत्युक्तम् । अथ पुनः ये उत्तरं दक्षिणं च एतौ पन्थानौ न विदुः, उत्तरस्य दक्षिणस्य वा पथः प्रतिपत्तये ज्ञानं कर्म वा नानुतिष्ठन्तीत्यर्थः;
In plain words
Even the gods themselves stand behind words like 'smoke' — what the departed actually reach is the deity, not the mere vapor. And every stage along this road works the same way: each deity is only ever a carrier, passing the traveler on to the next. From smoke to night, and the god of night; from there to the waning half of the month, and its god; from there through the six months while the sun swings south, each month handing them to its own particular god. From the months, to the world of the ancestors; from there, to the moon. And on the moon, of all things, they become food. Just as priests here on earth press King Soma and say to it, 'swell, wane,' then drink it — that is exactly what the gods do to these people once they reach the moon: masters feasting on their servants. But 'swell, wane' was never really a magic formula; it simply describes what happens when the priest keeps topping up the Soma in the cup and keeps drinking it down, again and again. In the same way, the gods keep restoring these embodied souls on the moon and keep drawing on them, portioning out to each exactly the reward their past deeds earned — that restoring is itself their 'swelling', and the gods feed on it the way the priests feed on Soma's own swelling. But eventually the merit that bought them this stay on the moon runs dry, and the moment it does, they dissolve into ordinary space — the space everyone already knows. Those waters — what scripture calls 'faith' — had been poured as an offering into the fire of heaven and turned into the very substance of Soma; from them a body of water was built for these souls to be used through on the moon. Once their merit is spent, that body melts away exactly the way a snowball melts in the sun, thinning out until it is barely more than space itself. That is what is meant by the line 'they merge into this very space.' From there the wind picks them up and scatters them here and there through the sky. Scripture puts it in four words: from space, to wind. From wind they become rain, offered — so scripture says — into the fire of the rain-god himself. As rain they fall to this earth, and once here, they become the food growing in the ground — rice, barley, all of it — because, as scripture says, rain poured into the fire here below is what produces grain. That grain, once eaten, is offered again, this time into the fire of a man's body, and turns to semen; the semen, in turn, is offered into the fire of a woman's body; and from that, at last, a child is born — one who will grow up and take his own turn tending the sacred fire. And then the whole circuit starts again: smoke, night, the moon, back to this earth, and around once more — endlessly, like water-pots hauled up and dumped by a turning wheel, because they never learned the one thing, brahman, that would have carried them onto the higher path or freed them outright. As scripture says: whoever still wants things simply keeps going round. And then there is a second kind of person who knows neither road at all, north or south, and so takes up neither the knowledge nor the ritual action that would lead to either one.
Close to the Sanskrit
Even the deities themselves are meant by the words 'smoke' and so on; that is, the departed attain the deity of smoke — this is the meaning; and the deities are, in just the same way, mere conveyors. From smoke, to night, to the deity of night; from that, to the waning fortnight, to the deity of the waning fortnight; from that, to the six months during which the sun travels toward the south, they attain the particular deities of those months. From the months, to the world of the fathers; from the world of the fathers, to the moon. Having reached the moon, they become food; having become food there — just as, here, in the sacrifice, the priests consume King Soma, saying 'swell, wane', so too the gods consume and enjoy these ritual-performers who have reached the moon, the way masters consume their servants. 'Swell, wane' is not a mantra; what then? Having repeatedly caused what stands in the cup to swell, and having brought about its waning by consuming it, they consume it again and again — this is the meaning. In the same way the gods too, in the world of the moon, giving repeated rest to these ritual-performers who have obtained bodies there and become mere instruments, bestowing on them a fruit that matches their action — for that itself is their swelling — the gods enjoy these beings-become-instruments the way one enjoys the swelling of Soma. When, at whatever time, that action characterized by sacrifice, giving, and so on, which procures the world of the moon for these ritual-performers, comes to an end, passes away, is exhausted — this is the meaning — then they merge into this very familiar space. Those waters, denoted by the word 'faith,' which were offered as oblation into the fire of the heavenly world and transformed into the form of Soma — by which, in the world of the moon, a body made of water was built up for the enjoyment of the ritual-performers — those waters, from the exhaustion of that merit, dissolve like a lump of snow through contact with heat; having dissolved, being subtle, they become as if made of space; and this is what is meant by the statement, 'they merge into this very space.' Those ritual-performers, again, having that same subtle body, are carried hither and thither by the fore-wind and the like, moving through the intermediate space; this is stated as, 'from space, to wind.' From wind, they attain rain; this is stated as, 'they offer King Soma into the fire of Parjanya.' From that, having become rain, they fall onto this earth. Having reached the earth, they become food such as rice, barley, and so on; this is stated as, 'in this world, they offer rain into the fire; from that oblation, food comes into being.' They are then offered again, having become food, into the fire that is a man, in the emission of semen; from that, having become semen, they are offered into the fire that is a woman; from that, they are born; those who rise up toward the world — that is, rising up into the world, they take up the practice of the agnihotra and other rites. Then, by way of smoke and so on, again and again to the world of the moon, and again to this world — thus these ritual-performers revolve on and on, having become a wheel, they whirl round like a water-wheel — this is the meaning — not knowing the brahman that leads either to the northern path or to immediate liberation. This has been stated: 'thus indeed the one who desires wanders in transmigration.' Now again, those who know neither of these two paths, the northern and the southern, undertake neither the knowledge nor the action that is the means to attaining the northern or the southern path — this is the meaning.
Bṛhadāraṇyakopaniṣadbhāṣyam· Leaf 10.114· bhāṣya
ते किं भवन्तीत्युच्यते— ते कीटाः पतङ्गाः, यदिदं यच्चेदं दन्दशूकं दंशमशकमित्येतत्, भवन्ति । एवं हि इयं संसारगतिः कष्टा, अस्यां निमग्नस्य पुनरुद्धार एव दुर्लभः । तथा च श्रुत्यन्तरम्— 'तानीमानि क्षुद्राण्यसकृदावर्तीनि भूतानि भवन्ति जायस्व म्रियस्व' इति । तस्मात्सर्वोत्साहेन यथाशक्ति स्वाभाविककर्मज्ञानहानेन दक्षिणोत्तरमार्गप्रतिपत्तिसाधनं शास्त्रीयं कर्म ज्ञानं वा अनुतिष्ठेदिति वाक्यार्थः ; तथा चोक्तम्— 'अतो वै खलु दुर्निष्प्रपतरं तस्माज्जुगुप्सेत' इति श्रुत्यन्तरात् मोक्षाय प्रयतेतेत्यर्थः । अत्रापि उत्तरमार्गप्रतिपत्तिसाधन एव महान् यत्नः कर्तव्य इति गम्यते, 'एवमेवानुपरिवर्तन्ते' इत्युक्तत्वात् । एवं प्रश्नाः सर्वे निर्णीताः ; 'असौ वै लोकः' इत्यारभ्य 'पुरुषः संभवति' इति चतुर्थः प्रश्नः 'यतिथ्यामाहुत्याम्' इत्यादिः प्राथम्येन ; पञ्चमस्तु द्वितीयत्वेन देवयानस्य वा पथः प्रतिपदं पितृयाणस्य वेति दक्षिणोत्तरमार्गप्रतिपत्तिसाधनकथनेन ; तेनैव च प्रथमोऽपि—अग्नेरारभ्य केचिदर्चिः प्रतिपद्यन्ते केचिद्धूममिति विप्रतिपत्तिः ; पुनरावृत्तिश्च द्वितीय. प्रश्नः— आकाशादिक्रमेणेमं लोकमागच्छन्तीति ; तेनैव— असौ लोको न संपूर्यते कीटपतङ्गादिप्रतिपत्तेश्च केषांचिदिति, तृतीयोऽपि प्रश्नो निर्णीतः ॥
In plain words
So what do they become? A small, crawling, short-lived thing — a worm, a moth, whatever bites, whatever buzzes and stings for a season and dies. This road through birth after birth is genuinely bad news, and once you are this far down in it, climbing back out is close to impossible. Another scripture says exactly this: these small creatures cycle through again and again, told simply, be born, die. So give it everything you have, whatever you're capable of — set aside the merely instinctive living and thinking you were born with, and take up instead the scripturally taught action or knowledge that actually opens the southern path or the northern one. That is what this whole passage is telling you to do. Elsewhere scripture says the same thing more sharply: nothing is harder to break free of than this, so let it fill you with dread — meaning, strive for freedom itself. And notice where the greater effort belongs: toward the northern path especially, since we have already been told plainly that otherwise a person just goes on revolving. With that, every one of the five questions is answered. The passage running from 'that world' to 'a person comes to be' answers the fourth question directly. The fifth is answered along the way, by explaining how one actually enters the path of the gods or the path of the fathers — and that same explanation quietly answers the first question too: some, starting from the fire, reach the flame, others the smoke, which was the very disagreement the first question raised. The second question, about coming back, is answered by tracing the descent, step by step from space downward, into this world. And that same account answers the third: the other world is never overcrowded, because some beings never even arrive there — they fall instead into the bodies of worms and moths.
Close to the Sanskrit
What do they become? — this is explained: they become insects, moths, and whatever else there is of this kind — biting reptiles, gadflies, mosquitoes. For this course of transmigration is truly wretched; for one sunk in it, a way back up is hard indeed to find. So too another scripture says: 'these small creatures, cycling back again and again, are told: be born, die.' Therefore, with all one's effort, according to one's ability, giving up the merely natural action and knowledge one is born with, one should undertake the scripturally enjoined action or knowledge that is the means to attaining the southern or the northern path — this is the meaning of the passage. So too it is said: 'nothing is harder to escape than this; therefore one should recoil from it' — from another scripture; the meaning is that one should strive for liberation. Here too it is understood that great effort in particular should be made toward the means of attaining the northern path, because it has already been said, 'thus indeed they go on revolving.' In this way all the questions have been settled. From 'that world, indeed' up to 'a person comes to be' answers the fourth question, 'at which oblation...' and so on, primarily. The fifth question, however, is answered secondarily, by the exposition of the means of attaining the path of the gods or the path of the fathers. And by that very exposition the first question too — 'beginning from Agni, some attain the flame, some the smoke' — that difference is resolved. The second question, about the return again, is resolved by showing that they come back to this world in due sequence beginning from space. And by that same account, the third question too is resolved: that world is never filled up, because some fall instead into the state of insects, moths, and the like.