Text 5 

sri-bhagavan uvaca
pasya me partha rupani
sataso ’tha sahasrasah
nana-vidhani divyani
nana-varnakritini ca

Translation

The Supreme Personality of Godhead said: My dear Arjuna, O son of Pritha, see now My opulences, hundreds of thousands of varied divine and multicolored forms. 

Commentary by Srila Prabhupada 

Arjuna wanted to see Krishna 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 Krishna is manifested and nonmanifested. It is not eternally situated in the spiritual sky like Krishna’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 Krishna in this way, Krishna reveals this form. This universal form is not possible to be seen by any ordinary man. Krishna must give one the power to see it.

Commentary by Sri Visvanatha Cakravarti Thakur

"First I will show him that form described in the purusa sukta as sahasra-sirsa purusah sahasraksah sahasrapat: that form with a thousand heads, a thousand eyes and a thousand feet. It is my own expansion, the first purusa avatara (Maha Visnu), the antaryami of prakrti. Later, by having the necessary qualification, I will show him my form of time." Considering in this way in his mind, the Lord faced Arjuna, telling him to pay attention. Thus he speaks this verse.

"See these hundreds and thousands of forms (rupani). In my one form, my svarupa, see hundreds of my svarupas, which are my vibhutis."