Because of the resounding vibrations of the denizens of heaven singing in the caves, the lions there, being very proud of their strength, roar with unbearable envy, thinking that another lion is roaring in that way.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
यत्र सङ्गीतसन्नादैर्नदद्गुहममर्षया । अभिगर्जन्ति हरयः श्लाघिनः परशङ्कया
yatra saṅgītasannādairnadadguhamamarṣayā | abhigarjanti harayaḥ ślāghinaḥ paraśaṅkayā
SB 8.2.6