Bhashya
ब्दसामर्थ्यात् कुत्रचित् तस्मै इत्येकवचनसामर्थ्यात् एक एवव्यूहः प्रतीयते ।स च द्विविधः कचिदसाधारणायुधैः तत्तद्दे-वतागम्यः प्रतीयते कचिच्च विश्वरूपः तेनैव न्यायेन उभय-त्रापि नृसिंहाकारः योगारूढ. अधस्तनहस्ताभ्यां वरदाभय-हस्त. उपरितनाभ्यां तत्तद्देवतायुधधारी कचिच्छङ्खचक्रगदा-धारी च इत्येतत्सर्वं स्पष्टं करिष्यामः ।यथा अत्रैव नृसिं-हाकारव्यूहा ब्रह्मविष्णुमहेश्वरात्मकाः स्रुक्स्रुवशङ्खचक्रपिना-कत्रिशूलैरायुधैर्गम्यन्ते नृसिंहात्मकः पुरुषव्यूहः द्विभुजःदश हस्त्या अङ्गुलयः दश पाद्याः यावानेव पुरुषः, इतिश्रुतेः ।अत ऊर्ध्वं सर्वे नृसिंहव्यूहाश्चतुर्भुजाः नृसिंहात्मकाश्चईश्वरव्यूह. ईश्वरायुधगम्यः पूर्वेषां पञ्चानां यथासंख्यं पञ्च-शक्तिव्यूह. सरस्वतीश्रीगौरीप्रकृतिविद्यात्मिकाः स्त्रियः स्वा-युधैर्गम्याः एवं मूलमन्त्राक्षरेषु दशसु ऐशानीं दिशमारभ्यप्रणवसंपुटितेषु सर्वाभरणयुक्ताः श्वेतरूपा उपास्याः ।एवंवक्ष्यमाणाः सर्वे व्यूहाः यथासंख्यं मूलमन्त्राक्षरेषु उपा-स्या. ।प्रणवव्यूहः एकेन प्रणवाक्षरेण वक्षसि चिह्नितः प्रण-वचतुष्टयमात्रः वासुदेवविग्रहः सशाखवेदविग्रहः पञ्चाग्नि-विग्रह. सप्तव्याहृतिविग्रहः अष्टलोकपालविग्रहः वसुरुद्रादि-त्याष्टग्रहपञ्चमहाभूतविग्रहाः एकैकस्मिन्नृसिंहव्यूहे यथासंख्य-मन्तर्भूताः उपास्याः इति दश व्यूहाः विश्वरूपाः उपास्याः ।कालमनुमृत्युयमान्तकप्राणसूर्यसोमविराट्पुरुषजीवरूपचेतनाचेतनसर्वात्मका इत्येते व्यूहाः अविश्वरूपाः तत्तदसाधारणरूपगम्याः एवमेकैकव्यूहः उपास्यः तेन तेन मन्त्रेण स्तुत्यः ततो देवः स्वात्मानं स्वकीयं रूपं विश्वरूपम् अविश्वरूपं च यथायोग्यं दर्शयति ।यस्मादेवं तस्मात् य उपासकः एतैर्मन्त्रैः नित्यं नियमेन स्तौति, स देवं विश्वरूपमविश्वरूपं च पश्यति साक्षात्करोति ।सोऽमृतत्वमित्यादि महोपनिषदित्यन्तं स्पष्टार्थम् ।तत्र अमृतत्वं च गच्छतीति फलस्य द्विरभ्यासः स्तुतिमात्रादेव परमफलावाप्तिं मन्त्राणां च सामर्थ्यं दर्शयति ।महोपनिषच्छब्दः प्रणवबाहुल्यमिति सर्वं निर्मलम् ॥
In plain words
Read the fragment above with what came before it: only one form is meant, and that form comes in two guises. Sometimes it is picked out by its own set of weapons, tied to one deity; sometimes it wears the whole universe as its shape. Either way, it is Narasiṃha, seated in stillness — two hands showing 'do not be afraid, receive what you need' and two hands holding whatever a particular deity carries, and sometimes conch, discus and mace together. All of this will be spelled out. Here the vision widens: these Narasiṃha-forms wear the nature of Brahmā, Viṣṇu, and Śiva at once, known by their tools — ladle, spoon, conch, discus, bow, trident. As the cosmic Person he is two-armed, his measure the very measure Śruti gives the Person — every finger, every foot, exactly enough. Above that level, every Narasiṃha-form grows four arms, carries the Lord's own weapon, and becomes the Lord's own emanation. And paired with those, five goddesses — Sarasvatī, Śrī, Gaurī, Prakṛti, Wisdom herself — each known by what she carries. Placed around the ten root syllables, beginning in the northeast, bracketed by Om on both sides, dressed in every ornament, white as moonlight — these are what a person meditates on. One single syllable of Om marks his chest, and in that mark the whole Veda, its branches, the five sacred fires, the seven sacred utterances, the eight guardians of the world, the Vasus, the Rudras, the Ādityas, the eight planets, the five elements — all of it folds into each single Narasiṃha, waiting to be worshipped as the universe itself. But there is another register too: Time, Manu, Death, Yama, the Ender, the breath of life, sun and moon, the cosmic Person, the individual soul, everything living and everything still — these emanations wear no universal face; each is known only by what makes it distinct. Either way, each form gets its own worship, its own mantra of praise, and the god answers by showing exactly the face that fits — sometimes the one form, sometimes the whole universe. And so whoever keeps this practice, praising steadily, without lapse, with these very mantras, actually sees the god — both as the universe and as the one particular form — and knows him, not as an idea, but directly. 'He attains immortality', repeated twice, is not padding: it is the text insisting that praise by itself, on its own, delivers the highest reward — that is how much power lives in these mantras. And the very word for 'great secret teaching' is really just a way of saying: Om, poured through everything.
Close to the Sanskrit
...by the force of the word, in some place, [and] by the force of the singular in 'tasmai', only one emanation is understood. And that is of two kinds: in some cases it is understood as reachable through this or that deity by uncommon weapons, and in some cases it is universal-formed; by that same principle, in both cases it is Narasiṃha in form, seated in yoga. With the two lower hands, the boon-granting and fear-dispelling gestures; with the two upper hands, the holder of this-or-that deity's weapon, in some cases the holder of conch, discus and mace — all this we will make clear. Just as, here itself, the Narasiṃha-form emanations, having the nature of Brahmā, Viṣṇu and Maheśvara, are recognized by the weapons — ladle, spoon, conch, discus, Śiva's bow and tridents — the Person-emanation in the nature of Narasiṃha is two-armed: ten are the finger-measures by the cubit, ten are the foot-measures, 'exactly as great as the Person is' — so says the Śruti. Beyond this, all Narasiṃha-emanations are four-armed and, being of Narasiṃha's nature, are also the Lord's emanation, reached through the Lord's weapon. Corresponding to the previous five, respectively, the five Power-emanations — women having the nature of Sarasvatī, Śrī, Gaurī, Prakṛti and Vidyā — are recognized by their own weapons. Thus in the ten root-mantra syllables, beginning from the northeast direction, enclosed within Om, adorned with all ornaments, of white form, they are to be worshipped. Thus all the emanations about to be described are, correspondingly, to be worshipped in the root-mantra syllables. The Om-emanation, marked on the chest by a single syllable of Om, consisting of exactly four Oms, is the embodiment of Vāsudeva, the embodiment of the Veda with its branches, the embodiment of the five fires, the embodiment of the seven utterances, the embodiment of the eight guardians of the quarters, the embodiments of the Vasus, Rudras, Ādityas, the eight planets and the five great elements — included respectively within each single Narasiṃha-emanation, they are to be worshipped. Thus these ten emanations, being universal-formed, are to be worshipped. Having the nature of Time, Manu, Death, Yama, the Ender, the vital breath, the Sun, the Moon, the cosmic Virāṭ-Person, the individual soul in form, the sentient and insentient, all — these emanations are non-universal-formed, recognized through their own distinctive forms. Thus each single emanation is to be worshipped, is to be praised by its own respective mantra. Then the deity shows his own self, his own particular form, the universal form and the non-universal form, as is fitting. Since it is thus, therefore whoever, as a worshipper, praises with these mantras constantly and with discipline, he sees the deity in universal form and non-universal form, and realizes him directly. 'He [attains] immortality' and so on, up to 'the great secret teaching', is clear in meaning. There, the twofold repetition of the result — 'and he attains immortality' — shows the attainment of the supreme fruit from praise alone, and the efficacy of the mantras. The word 'mahopaniṣad' means the abundance of Om — thus everything here is clear.