Yoga Sūtra Chapter Three verse 41

श्रोत्राकाशयोः संबन्धसंयमात् दिव्यं श्रोत्रम् ॥४१॥

śrotra-ākāśayoḥ saṃbandha-saṃyamāt-divyaṃ śrotram ||41||

From complete restraint of connection between ear and space;
divine hearing.

śrotra - sense of hearing; earākāśa - space; ether; subtle and ethereal fluid; sky, atmospheresaṃbandha - connection, binding or joining together, close union or associationsaṃyama - complete restraintdivya - divine