Srimad Bhagavatam Canto 03, Chapter 06, Text 17

SB 3.6.17

karnav asya vinirbhinnau
 dhisnyam svam vivisur disah
srotrenamsena sabdasya
 siddhim yena prapadyate
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
When the ears of the gigantic form became manifested, all the controlling deities of the directions entered into them with the hearing principles, by which all the living entities hear and take advantage of sound.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
The ear is the most important instrument in the body of the living entity. Sound is the most important medium for carrying the message of distant and unknown things. The perfection of all sound or knowledge enters through the ear and makes one’s life perfect. The entire Vedic system of knowledge is received by aural reception only, and thus sound is the most important source of knowledge.
Srimad Bhagavatam Canto 03, Chapter 06, Text 16
Srimad Bhagavatam Canto 03, Chapter 06, Text 18