ब्रह्म वा इदमग्र आसीदेकमेव ।तदेकं सन्न व्यभवत् ।तच्छ्रेयो रूपमत्यसृजत क्षत्रं, यान्येतानि देवत्रा क्षत्राणीन्द्रो वरुणः सोमो रुद्रः पर्जन्यो यमो मृत्युरीशान इति ।तस्मात्क्षत्रात्परं नास्ति ।तस्माद्ब्राह्मणः क्षत्रियं अधस्तादुपास्ते राजसूये ।क्षत्र एव तद्यशो दधाति ।सैषा क्षत्रस्य योनिर्यद्ब्रह्म ।तस्माद्यद्यपि राजा परमतां गच्छति ब्रह्मैवान्तत उपनिश्रयति स्वां योनिम् ।य उ एनं हिनस्ति स्वां स योनिमृच्छति ।स पापीयान् भवति यथा श्रेयांसं हिंसित्वा ॥बृह. १,४.११ ॥
In plain words
In the beginning this was Brahman, one only. Being one, it did not flourish. It brought forth a better form, the ruling power — those who are rulers among the gods: Indra, Varuṇa, Soma, Rudra, Parjanya, Yama, Mṛtyu, Īśāna. Therefore there is nothing higher than the ruling power; and therefore at the Rājasūya sacrifice the brahmin sits below the man of the ruling class and confers that glory upon the ruling power. But the womb of the ruling power is the priestly power. Therefore, though a king reaches the summit, at the end he takes refuge in the priestly power, his own womb. And whoever injures it strikes at his own womb, and becomes the worse, as one who has injured his better.
The commentators
Bṛhadāraṇyakopaniṣadbhāṣyam· bhāṣya
ब्रह्म वा इदमग्र आसीत्—यदग्निं सृष्ट्वा अग्निरूपापन्नं ब्रह्म—ब्राह्मणजात्यभिमानात् ब्रह्मेत्यभिधीयते—वै, इदं क्षत्रा- दिजातम्, ब्रह्मैव, अभिन्नमासीत्, एकमेव—न आसीत्क्ष- त्रादिभेदः । तत् ब्रह्मैकं क्षत्रादिपरिपालयित्रादिशून्यं सत्, न व्यभवत् न विभूतवत् कर्मणे नालमासीदित्यर्थः । तत- स्तद्ब्रह्म— ब्राह्मणोऽस्मि ममेत्थं कर्तव्यमिति ब्राह्मणजातिनि- मित्तं कर्म चिकीर्षुः आत्मनः कर्मकर्तृत्वविभूतये, श्रेयोरूपं प्रशस्तरूपम्, अति असृजत अतिशयेन असृजत सृष्टवत् । किं पुनस्तत्, यत्सृष्टम् ? क्षत्रं क्षत्रियजातिः ; तद्व्यक्ति- भेदेन दर्शयति— यान्येतानि प्रसिद्धानि लोके, देवत्रा देवेषु, क्षत्राणीति— जात्याख्यायां पक्षे बहुवचनस्मरणात् व्यक्तिबहुत्वाद्वा भेदोपचारेण—बहुवचनम् । कानि पुनस्ता- नीत्याह— तत्राभिषिक्ता एव विशेषतो निर्दिश्यन्ते— इन्द्रो देवानां राजा, वरुणो यादसाम्, सोमो ब्राह्मणानाम्, रुद्रः पशूनाम्, पर्जन्यो विद्युदादीनाम्, यमः पितृणाम्, मृत्युः मपि क्षत्रियः पाप एव क्रूरत्वात्, आत्मप्रसवहिंसया सुत- राम्; यथा लोके श्रेयांसं प्रशस्ततरं हिंसित्वा परिभूय पापतरो भवति, तद्वत् ॥
In plain words
Brahman was indeed this in the beginning. Brahman here is the Brahman that, having created Fire, had taken on the form of Fire; it is called Brahman because it identified itself with the brāhmaṇa class. All this, the kṣatriya and the other classes, was Brahman alone, undivided; it was one only, with no distinction yet of kṣatriya and the rest. Being one, with no kṣatriya or any other to protect it, that Brahman did not flourish: it was not equal to its work. Then that Brahman, wishing to do the work that belongs to the brāhmaṇa class, thinking, 'I am a brāhmaṇa; this is what I must do', and to grow in its own power as one who performs rites, projected forth, and projected forth abundantly, an excellent form, a form worthy of praise. What was it that it created? The kṣatra, the ruling class. The text shows it through its individual members: those well known in the world as the ruling powers among the gods; the plural, because a class name may be put in the plural, or because the individuals are many. Who are they? It names in particular those who have been consecrated: Indra, king of the gods; Varuṇa, of the creatures of the waters; Soma, of the brāhmaṇas; Rudra, of the animals; Parjanya, of lightning and its kin; Yama, of the ancestors; Mṛtyu … even a kṣatriya is sinful for his cruelty, and all the more when he harms his own source; just as in the world one who harms and humiliates someone better and more worthy than himself becomes the more sinful.
Close to the Sanskrit
Brahman indeed was this in the beginning—having created Agni, Brahman having attained the form of Agni is designated as Brahman due to identification with the brāhmaṇa caste—'indeed', this, the kṣatriya and the other classes, was Brahman alone, undivided; 'one' alone: there was no distinction of kṣatriya and the rest. That Brahman, being one, being without a protector such as the kṣatriya and the rest, 'did not expand': it did not become mighty, that is, it was not equal to its work. Then that Brahman, wishing to do the work that belongs to the brāhmaṇa class, thinking 'I am a brāhmaṇa; this is what I must do', for the growth of its own power as a doer of rites, 'projected forth' (ati asṛjata), projected forth exceedingly, created, 'an excellent form', a praiseworthy form. What, then, was it that was created? The kṣatra, the kṣatriya class. It shows it by the distinction of individuals: 'those which are these', well known in the world, 'among the gods' (devatrā), 'ruling powers'; the plural, because on one view the plural is taught for the name of a class, or, because the individuals are many, by a figurative distinction. Which are they? He says: there, those who have been consecrated are specifically named: Indra, king of the gods; Varuṇa, of the water-creatures; Soma, of the brāhmaṇas; Rudra, of the animals; Parjanya, of lightning and the rest; Yama, of the ancestors; Mṛtyu … even a kṣatriya is sinful, because of cruelty, and all the more by harming his own source; just as in the world one becomes more sinful by harming and humiliating one who is better, more worthy of praise, so it is.