सो हेयमीक्षां चक्रे कथं नु मात्मन एव जनयित्वा सम्भवति ।हन्त तिरोऽसानीति ।सा गौरभवद्वृषभ इतरः ।तां समेवाभवत् ।ततो गावोऽजायन्त ।वडवेतराभवदश्ववृष इतरः ।गर्दभीतरा गर्दभ इतरः ।तां समेवाभवत् ।तत एकशफमजायत ।अजेतराभवद्बस्त इतरः ।अविरितरा मेष इतरः ।तां समेवाभवत् ।ततोऽजावयो ऽजायन्त ।एवमेव यदिदं किञ्च मिथुनमा पिपीलिकाभ्यस्तत्सर्वमसृजत ॥बृह. १,४.४ ॥
In plain words
She thought, "How can he couple with me after having brought me forth from himself? Come, let me hide." She became a cow; he became a bull and coupled with her, and thence cattle were born. She became a mare, he a stallion; she a she-ass, he a he-ass; and he coupled with her, and thence one-hoofed animals were born. She became a she-goat, he a he-goat; she a ewe, he a ram; and he coupled with her, and thence goats and sheep were born. Thus he brought forth everything here that goes in pairs, down to the ants.
The commentators
Bṛhadāraṇyakopaniṣadbhāṣyam· bhāṣya
तरावभवत् अश्ववृष इतरः । तथा गर्दभीतरा गर्दभ इतरः । तत्र वडबाश्ववृषादीनां संगमात्तत एकशफम् एकखुरम् अश्वाश्वतरगर्दभाख्यं त्रयमजायत । तथा अजा इतराभवत्, बस्तश्छाग इतरः । तथाविरितरा, मेष इतरः । तां समे- वाभवत् । तां तामिति वीप्सा । तामजां तामविं चेति समभवदेवेत्यर्थः । ततोऽजाश्वावयश्चाजावयोऽजायन्त । एव- मेव यदिदं किंच यत्किंचेदं मिथुनं स्त्रीपुंसलक्षणं द्वन्द्वम्, आ पिपीलिकाभ्यः पिपीलिकाभिः सह अनेनैव न्यायेन तत्सर्वमसृजत जगत्स्रष्टृवान् ॥
In plain words
She turned into a mare and he into a stallion; she became a she-donkey and he a male donkey. From the union of horses, donkeys, and mares came solid-hoofed animals such as horses, mules, and donkeys. Likewise, she-goats and he-goats mated, as did ewes and rams. The text repeats 'her and her' to show that he united with every individual female. From these unions, goats, sheep, and all other creatures were born. In this exact manner, acting as the creator of the universe, he brought forth every male-female pair down to the smallest ant.
Close to the Sanskrit
The other became a mare, a stallion the other. Thus she-donkey the other, donkey the other. There, from the union of mares, stallions and others, a triad of solid-hoofed beings—horses, mules, and donkeys—was born. Likewise, she-goat became the other, buck-goat the other. Ewe the other, ram the other. He united with her. The repetition 'her, her' signifies distribution: he united with that she-goat and that ewe indeed. Thence goats, horses, sheep and goats-and-sheep were born. In this very way whatever male-female pairs exist here, down to ants, all that he created acting as the creator of the world.