Visvarupa Darsana Yoga-Bhagavad Gita Chapter 11 [The Vision of the Universal Form]
Krishna Said > Shaloka: 6
O best of the Bharatas, see here the different manifestations of Adityas, Rudras, and all the demigods. Behold the many things which no one has ever seen or heard before.
Even though Arjuna was a personal friend of Krishna and the most advanced of learned men, it was still not possible for him to know everything about Krishna. Here it is stated that humans have neither heard nor known of all these forms and manifestations. Now Krishna reveals these wonderful forms.