TAITTIRĪYA UPANISHAD · 3.1

भृगुर्वै वारुणिः । वरुणं पितरमुपससार ।
अधीहि भगवो ब्रह्मेति । तस्मा एतत्प्रोवाच ।
अन्नं प्राणं चक्षुः श्रोत्रं मनो वाचमिति ।
तंहोवाच । यतो वा इमानि भूतानि जायन्ते ।
येन जातानि जीवन्ति ।
यत्प्रयन्त्यभिसंविशन्ति । तद्विजिज्ञासस्व । तद्ब्रह्मेति ।
स तपोऽतप्यत । स तपस्तप्त्वा ।

bhṛgurvai vāruṇiḥ । varuṇaṃ pitaramupasasāra ।
adhīhi bhagavo brahmeti । tasmā etatprovāca ।
annaṃ prāṇaṃ cakṣuḥ śrotraṃ mano vācamiti ।
taṃhovāca । yato vā imāni bhūtāni jāyante ।
yena jātāni jīvanti ।
yatprayantyabhisaṃviśanti । tadvijijñāsasva । tadbrahmeti ।
sa tapo’tapyata । sa tapastaptvā ।

Bhrigu, Varouna’s son, came unto his father Varouna and said “Lord, teach me the Eternal.” And his father declared it unto him thus “Food and Prana and Eye and Ear and Mind — even these.” Verily he said unto him “Seek thou to know that from which these creatures are born, whereby being born they live and to which they go hence and enter again; for that is the Eternal.” And Bhrigu concentrated himself in thought and by the askesis of his brooding

Sri Aurobindo · CWSA 18, p. 225