Srimad Bhagavatam Canto 10, Chapter 15, Text 23

   SB 10.15.23

so ’ti-viryo ’suro rama
 he krsna khara-rupa-dhrk
atma-tulya-balair anyair
 jnatibhir bahubhir vrtah
 
Translation: 
 
O Rama, O Krsna! Dhenuka is a most powerful demon and has assumed the form of an ass. He is surrounded by many friends who have assumed a similar shape and who are just as powerful as he.
Srimad Bhagavatam Canto 10, Chapter 15, Text 22
Srimad Bhagavatam Canto 10, Chapter 15, Text 24