प्राणो ब्रह्मेति व्यजानात् ।प्राणाद्ध्येव खल्विमानि भूतानि जायन्ते ।प्राणेन जातानि जीवन्ति ।प्राणं प्रयन्त्यभिसंविशन्तीति ।तद्विज्ञाय पुनरेव वरुणं पितरमुपससार ।अधीहि भगवो ब्रह्मेति ।तँ होवाच ।तपसा ब्रह्म विजिज्ञासस्व ।तपो ब्रह्मेति ।स तपोऽतप्यत ।स तपस्तप्त्वा ॥ १ ॥
In plain words
he knew that breath is Brahman; for from breath indeed are these beings born, by breath, being born, they live, and into breath, departing, they enter. Having known that, he came again to his father Varuṇa and said, "Sir, teach me Brahman." He said to him, "Seek to know Brahman by austerity; austerity is Brahman." So he performed austerity; and having performed austerity,