Bhashya
देवा अकृतपुरश्चरणा वै मृत्योरबिभयुः ।ते उपासका देवाःमृत्योः मरणहेतोर्वैवस्वतात् , स च मृत्युः पाप्मपूर्वक इतिपाप्मभ्यः, तच्च पापं संसारपूर्वकमिति संसाराच्च अज्ञान-भयात् समस्ताद्व्यस्ताद्वितयात् अबिभयुः भयमागच्छन्-इति प्रत्येकं संबध्यते ।द्विविधा हि उपासका देवाःमुमुक्षवः अमुमुक्षवश्चेति ; तत्र मुमुक्षूणां त्रितयं समुच्चितंविशेषणम् ।अमुमुक्षूणां ह्यकृतपुरश्चरणानां व्यस्तं द्वितयंविशेषणम्, केचन केवलं मृत्योर्जयमेव कामयन्ते, केचनपाप्मन एव जयम्, अन्ये तु त्रितयजयम् ।ते द्विविधा देवाःप्रजापतिमुपाधावन्, उपपूर्वको धावतिः पूजामाह, उप स-मीपमेत्य प्रजापतिमपूजयन् स्तुतिशुश्रूषादक्षिणाभिश्च ।तेभ्योदेवेभ्यः प्रीतः प्रजापति एतं मन्त्रराजमित्याद्यानुष्टुभमित्य-न्तं सर्वमुक्तार्थं प्रायच्छत् प्रादात् ।तेन प्रदानेन वै स प्रजा-पतिः मृत्युमजयत् ।देवा अपि मृत्युमजयन् ।अजयन्नितिबहुवचनात् स इत्येकवचनात् उभयत्रापि प्रकृत्यर्थसंबन्धे प्राप्ते,यथायोग्यतत्तद् वचनं योज्यम् ।तथा तेनेत्यर्थप्राप्तं स्वीकरणंपरामृश्यते ।एतदुक्तं भवति—तेन प्रदानेन प्रजापतिः मृत्यु-मजयत् , तेन स्वीकारेण देवा मृत्युमजयन्निति ।कैश्चिदेवंव्याख्यातम्—समृत्युमिति समस्तं कृत्वा सह मृत्युना वर्ततेयदज्ञानं तत्तथोक्तम् , तन्न, पूर्वं तस्याप्रकृतत्वात् ।अथार्थप्राप्तंप्रकृतमिति चेत् , भवतु न कश्चिद्विरोधः ; किं तु दातुःफलं न संकीर्तितं स्यादिति दाता कथं प्रवर्तेत? दक्षिणा-दिभिरिति चेत् , न ।विरक्ते तु का वार्ता ।तस्मादुभयत्रा-पि फलवत्युपासनेयमिति व्याख्या ज्यायसी ।एवमुत्तरत्रापिव्याख्येयम्—पाप्मानं स संसारम् अतरत् अतरन्निति च ।य-स्मादिदमुभयत्र फलवत् , तस्माद्यः प्रागुक्तः उपासकः मृत्योःपाप्मभ्यः संसाराच्च बिभीयान् समस्ताद्व्यस्ताद्वितयाद्वयं गच्छे-त् , स प्रागुक्त उपासको गुरूपसर्पणेन एतं मन्त्रराजमित्यादि .स संसारं तरतीत्यन्तं स्पष्टार्थम् ।प्रतिगृह्णीयात् स्वीकुर्यादित्य-र्थः ।अनेनैतद्दर्शयति—मूलमन्त्रमात्रग्रहणे गुरूपसर्पणमावश्य-कम् ।सामप्रभृत्युपासनांशे गुरूपसर्पणाच्छ्रुतितः तद्व्याख्या-नाद्वेति विकल्पः, ‘तस्मादिदं साम येन केनचिदाचार्यमुखेन’इति श्रुतेः ।अत एव एतद्विषयरहस्यकल्पग्रन्थान् असमर्थश्चेत्गुरुमुखाच्छृणुयात् समर्थश्चेत्स्वयमेवावेक्षेत, मूलमन्त्रं सबीजंसशक्तिकं साङ्गं सन्यासं गुरुमुखात्स्वीकृत्य ।एवं प्रागुक्त-स्योपासकस्य मुमुक्षोः प्रागुक्तं त्रितयं विशेषणम् इतरस्य द्वितयं विशेषणम् उभयत्रापि स्तुत्युपनिषत्प्रतिपादितं स्तवनं तेषां व्यूहानामुपासनं साम्ना मूलमन्त्राभिव्यक्तिश्चेति त्रितयमप्येतत् पुरश्चरणरूपत्वात्साधारणम् ।
In plain words
The gods feared death -- and they feared it precisely because they had skipped the groundwork, the preliminary practice that should have come first. Look closer at what that fear really was: they feared death, which is only Yama, the cause of dying; they feared sin, because death itself is rooted in sin; they feared the whole turning wheel of saṃsāra, because sin itself is rooted in that wheel. Strip it back further and it is all one fear, born of ignorance -- whether you count the three causes together or take any two of them apart, the fear reaches into each. Now, meditating gods come in two kinds: those who want liberation, and those who do not. For the ones who want liberation, all three fears move as one bundled concern. For the others, who never did the groundwork, it splits -- some want only to beat death, some only to beat sin, others want to beat all three anyway. Both kinds went to Prajāpati. To 'run toward' with 'up' in front of it means, quite simply, to pay homage -- so they drew near and honored him with praise, with willing service, with gifts. And Prajāpati, moved by their devotion, gave them everything -- the whole passage, from 'the king of mantras' through to 'the Anuṣṭubh metre', whose meaning has already been unfolded. By that gift, Prajāpati himself conquered death. The gods, too, conquered death. Notice the grammar shifts -- 'they conquered' is plural, 'he' is singular -- but both point back to the same giving: Prajāpati conquered death by giving the mantra, the gods conquered death by receiving it. Some readers have tried to fuse 'death' into one word with what follows, reading it as 'the ignorance that travels with death' -- but that will not hold, because nothing here has set up ignorance as the topic. And even granting, for argument's sake, that the topic could be recovered from context, it still leaves a giver with no stated reward for giving -- so why would he ever give? Sacrificial fees will not answer that, either: a being beyond desire has no use for fees. So the only reading that actually works is the one where both giver and receiver profit -- and that is the better explanation. The very same logic carries the next line: 'he crossed over sin and saṃsāra,' 'they crossed over' -- read it the same way. And because the fruit holds in both directions, this is the rule for anyone who fears death, sin, and saṃsāra, whether as one weight or in parts: go to a teacher, and receive this mantra just as it was given. Receiving here simply means accepting it as one's own. And this teaches something important: to take up the root mantra at all, a teacher is not optional. For the portion built around the Sāma, there is a choice -- hear it from a teacher's living voice, or study a written explanation of it -- because scripture itself says this Sāma may come from any teacher's mouth whatsoever. So if you cannot work through the secret manuals on this yourself, listen to a teacher; if you can, study them on your own -- but only once you have first received the root mantra in full, its seed, its power, its ancillary parts, and its ritual placement, from a teacher's mouth. This, then, is the whole shape of it: for the seeker of liberation, all three fears stand together as one qualifying condition; for the other, they fall into a pair. But underneath both, the same three things are shared by every practitioner alike -- the hymn of praise taught in the Stuti-Upaniṣad, meditation on the deity's unfolding forms, and the root mantra brought into full voice through the Sāma. All three belong to everyone, because all three are simply the groundwork itself.
Close to the Sanskrit
The gods, without the preliminary practice done, indeed feared, [as regards] death. Those meditating gods [feared], [as regards] death -- the cause of dying, [that is,] Vaivasvata; and that death is preceded by sin, thus [they feared as regards] sins; and that sin is preceded by saṃsāra, thus [they feared as regards] saṃsāra as well -- out of the fear of ignorance, whether taken all together or as a pair taken separately -- 'they came to fear': this is to be connected with each [ablative] individually. For the meditating gods are of two kinds: those seeking liberation and those not seeking liberation. Among these, for the seekers of liberation, the triad is a combined qualifier. For the non-seekers, who have not performed the preliminary practice, the qualifier is the pair taken separately: some desire only the conquest of death alone, some only the conquest of sin, others the conquest of all three. Those two kinds of gods approached Prajāpati -- [the root] 'dhāv' preceded by 'upa' expresses worship: having drawn near, they worshipped Prajāpati with praise, service, and sacrificial gifts. Pleased with those gods, Prajāpati gave [them] this -- everything from 'the king of mantras', whose meaning has [already] been stated, up to 'in the Anuṣṭubh metre' -- he gave, he bestowed. By that giving indeed, that Prajāpati conquered death; the gods too conquered death. From the plural 'they conquered' and the singular 'he', since in both the connection with the sense of the agent is obtained, the number is to be applied as fitting in each case; likewise, by 'by that' the acceptance implied in the sense is recalled. This is what is meant: 'by that giving Prajāpati conquered death, by that acceptance the gods conquered death.' By some it has been explained thus: taking 'sa-mṛtyum' as a single compound, [it means] 'that ignorance which exists together with death' -- so termed; that is not [correct], because it was not previously the topic. If [one says]: 'it is the topic because obtained through the sense' -- let it be so, there is no contradiction; but then, since the giver's fruit would not be stated, how would the giver be moved to act? If [one says]: 'by sacrificial fees and the like' -- no. In the case of one who is dispassionate, what relevance has that? Therefore, in both cases, this is a fruitful meditation -- this explanation is superior. In the same way it is to be explained further on: 'he crossed over sin, [he crossed over] saṃsāra' and 'they crossed over' likewise. Since this is fruitful in both cases, therefore the aforementioned meditator, who should fear death, sins, and saṃsāra -- whether all together or should come to a fear from a pair taken separately -- that aforementioned meditator, by approaching a teacher, [should take] this [mantra, beginning] 'the king of mantras' and so on. [The passage] up to 'he crosses over saṃsāra' has a clear meaning. 'Should receive' means 'should accept' -- that is the meaning. By this he shows: in taking up merely the root mantra, approaching a teacher is necessary. In the portion of meditation beginning with the Sāma, there is an option -- from approaching a teacher and hearing it, or from an explanation of it -- since the Śruti says: 'therefore this Sāma [may be received] from the mouth of any teacher whatsoever.' For this very reason, if unable [to study] the secret ritual-treatises on this subject, one should hear [them] from the teacher's mouth; if able, one should examine them oneself -- [only] after having received the root mantra, with its seed, with its power, with its ancillary parts, and its ritual placement, from the teacher's mouth. Thus, for the aforementioned meditator who seeks liberation, the aforementioned triad is the qualifier; for the other, the pair is the qualifier. In both cases: the praise taught in the Stuti-Upaniṣad, the meditation on those arrays, and the manifestation of the root mantra through the Sāma -- this threefold [set] too is common [to both], because it has the character of the preliminary practice.