"A pure devotee does not like to see Krsna in any form except His form with two hands; a devotee must see His universal form by His grace, not with the mind but with spiritual eyes. To see the universal form of Krsna, Arjuna is told not to change his mind but his vision. The universal form of Krsna is not very important; that will be clear in the verses. Yet because Arjuna wanted to see it, the Lord gives him the particular vision required to see that universal form."
Devotees who are correctly situated in a transcendental relationship with Krsna are attracted by loving features, not by a godless display of opulences. The playmates of Krsna, the friends of Krsna and the parents of Krsna never want Krsna to show His opulences. They are so immersed in pure love that they do not even know that Krsna is the Supreme Personality of Godhead. In their loving exchange they forget that Krsna is the Supreme Lord. In the Srimad-Bhagavatam it is stated that the boys who play with Krsna are all highly pious souls, and after many, many births they are able to play with Krsna. Such boys do not know that Krsna is the Supreme Personality of Godhead. They take Him as a personal friend. The Supreme Person is considered the impersonal Brahman by great sages, as the Supreme Personality of Godhead by the devotees, and as a product of this material nature by ordinary men. The fact is that the devotee is not concerned to see the visva-rupa, the universal form, but Arjuna wanted to see it to substantiate Krsna's statement so that in the future people could understand that Krsna not only theoretically or philosophically presented Himself as the Supreme but actually presented Himself as such to Arjuna. Arjuna must confirm this because Arjuna is the beginning of the parampara system. Those who are actually interested to understanding the Supreme Personality of Godhead, Krsna, and who follow in the footsteps of Arjuna should understand that Krsna not only theoretically presented Himself as the Supreme, but actually revealed Himself as the Supreme."
Bhagavad-gita 8:9 Purport
"....Krsna in His universal form, which, although a transcendental form, is just manifested for the cosmic manifestation and is therefore subject to the temporary time of this material nature. As the material nature is manifested and not manifested, similarly this universal form of Krsna is manifested and nonmanifested. It is not eternally situated in the spiritual sky like Krsna's other forms. As far as a devotee is concerned, he is not eager to see the universal form, but because Arjuna wanted to see Krsna in this way, Krsna reveals this form. This universal form is not possible to be seen by any ordinary man. Krsna must give one the power to see it."
Bhagavad-gita 11:5 Purport
"Arjuna saw in that universal form unlimited mouths and unlimited eyes. It was all wondrous. The form was decorated with divine, dazzling ornaments and arrayed in many garbs. He was garlanded gloriously, and there were many scents smeared over His body. All was magnificent, all-expanding, unlimited. This was seen by Arjuna."
"Physical nature is known to be endlessly mutable. The universe is the cosmic form of the Supreme Lord, and I am that Lord represented as the Supersoul, dwelling in the heart of every embodied being.
Purport: The physical nature is constantly changing. Material bodies generally pass through six stages: they are born, they grow, they remain for some duration, they produce some by-products, they dwindle, and then they vanish. This physical nature is called adhibhuta. Because it is created at a certain point and will be annihilated at a certain point, the conception of the universal form of the Supreme Lord that includes all demigods and their different planets is called adhidaivata. The individual soul (jiva) accompanies the body. The Supersoul, a plenary representation of Lord Krsna, is called the Paramatma or adhiyajna and is situated in the heart. The word eva is particularly important in the context of this verse because by this word the Lord stresses that the Paramatma is not different from Him. The Supersoul, the Supreme Personality of Godhead, seated beside the individual soul, is the witness of the individual soul's activities and is the source of consciousness. The Supersoul gives the jiva an opportunity to act freely, and He witnesses his activities. The functions of all these different manifestations of the Supreme Lord automatically become clarified for the pure Krsna conscious devotee engaged in transcendental service of the Lord. The gigantic universal form of the Lord called adhidaivata is contemplated by the neophyte who cannot approach the Supreme Lord in His manifestation as Supersoul. The neophyte is advised to contemplate the universal form whose legs are considered the lower planets and whose eyes are considered the sun and moon, and whose head is considered the upper planetary system."
Bhagavad-gita 8:4 Purport
Bhaktivedanta Book Trust. HDG A.C. Bhaktivedanta Swami Srila Prabhupada.