Srimad Bhagavadgita Sadhaka Sanjivani -Swami Ramsukhdas
"Hearing this statement, Arjuna by offering praise and prayer to Him, requested Him to describe His divine glories. Similarly, by hearing the Lord's statement, that He stands supporting the whole universe with a single fragment of His self, Arjuna prays to the Lord to reveal to him, His cosmic form. If the Lord had not made this statement, Arjuna would have not prayed to Him, to reveal His cosmic form. It means, that the Lord by His own grace, wants to reveal to him His cosmic form.