आकश एव यस्यायतनं श्रोत्रं लोको मनो ज्योतिर्यो वै तं पुरुषं विद्यात्सर्वस्यात्मनः परायणं स वै वेदिता स्यात् ।याज्ञवल्क्य वेद वा अहं तं पुरुषं सर्वस्यात्मनः परायणं यमात्थ ।य एवायं श्रौतः प्रातिश्रुत्कः पुरुषः स एष ।वदैव शाकल्य तस्य का देवतेति ।दिश इति होवच ॥बृह. ३,९.१३ ॥
In plain words
"He whose dwelling is space, whose world is the ear, whose light is the mind — he who knows that person, the highest goal of every self, would truly be a knower, Yājñavalkya." "I do know that person, the highest goal of every self, of whom thou speakest. He is the person in hearing and in the echo. Speak on, Śākalya. Which is his deity?" "The quarters," he said.
The commentators
Bṛhadāraṇyakopaniṣadbhāṣyam· bhāṣya
आकाश एव यस्यायतनम् । य एवायं श्रोत्रे भवः श्रौत्रः, तत्रापि प्रतिश्रवणवेलायां विशेषतो भवतीति प्रातिश्रुत्कः, तस्य का देवतेति- दिश इति होवाच ; दिग्भ्यो ह्यसौ आध्यात्मिको निष्पद्यते ॥
In plain words
Space alone is his home. Call him 'auditory' because he arises right there in the ear; call him 'the echo-one' because he shows up exactly at the instant a sound comes back to you. Ask his god, and the answer is the directions themselves — because it's out of the four quarters that this inward self of hearing is born.
Close to the Sanskrit
'Space alone is his abode' — the one who arises in the ear is 'śrautra'; and since he arises there specially at the moment of an echo, he is 'prātiśrutka'. Of him, what is the deity? — 'The directions', he said; for it is from the directions that this inward counterpart comes to be.