In the Gita also, Arjuna extols the glories of the Lord at several places. The Lord also describes His glories. These are equivalent to the Mantra portion of the Vedas. Gita talks about Karma, its effects, and about Karma Yoga in detail. These cover the Brahmana portion of the Vedas. Gita talks about several internal disciplines of dhyana, japa, etc. Also, the glories of the Lord described to help in meditation on the Lord. These cover the Aaranyaka portion of the Vedas. Gita talks about the Ultimate Truth of Advaita in several places. This covers the Upanisad portion of the Vedas.
The first three parts of the Vedas are called Karma Kanda. The Upanisad part of the Vedas is called Jnana Kanda. They are also called Pravritti Maarga and Nivritti Maarga. The aim of the Karma Kanda is to prepare the aspirant towards Jnana Kanda. The Karma Kanda is called Yogashaastra. The Jnaana Kanda is called Brahmavidya. To emphasize that Gita covers both these, at the end of every chapter, it is mentioned “Iti Srimad Bhagavad Gitaasu, Upanisadsu, Brahmavidyaayaam, Yogashaastre, Sri Krishna Arjuna Samvaade, …”
The Srimad-Bhagavad-Gita occurs in the Bhisma Parva of the Mahabharata and comprises 18 chapters from the 25th to the 42nd, 700 shlokas(verses).
On hearing the Lord declaring that the entire Universe is held in a mere fraction of His being, Arjuna is desirous of seeing with his own eyes the form of the Lord that sustains the world system. Therefore, extolling the Lord and His teaching, Arjuna requests Him to grant him a direct vision of His Cosmic body.
MADANUGRAHAYA PARAMAM GUHYAMADHYATMA SAMJNITAM YATVAYOKTAM VACASTENA MOHOAYAM VIGATO MAMA
By the supremely profound words, on the discrimination of Self, that have been spoken by Thee out of compassion towards me, this my delusion is gone.
BHAVAPYAYAU HI BHOOTANAM SHRUTOU VISTARASHO MAYA TVATTAH KAMALAPATRAKSHA MAHATMYAMAPI CA AVYAYAM
Of Thee, O Lotus-eyed, I have heard at length, of the origin and dissolution of beings, as also Thy inexhaustible greatness.
EVAMETADYATHATH TVAMATMANAM PARAMESWARA DRASHTUMICHAMI TE ROOPAMAISHWARAM PURUSHOTTAMA
So it is, O Supreme Lord! as Thou hast declared Thyself, (still) I desire to see Thy Ishwara Form. O Supreme Purusa.
Krishna finding it appropriate to do this says:
Behold, My different celestial forms, of various colours and shapes, by hundreds and thousands. Behold the Adityas, the Vasus, the Rudras, the twin Aswins, and the Maruts; behold many wonders never seen before. See now , O Gudakesha, in this My body, the whole universe centered in one(IHAIKASTHAM JAGATKRTSNAM) including the moving and the unmoving and all else that you desire to see. But you can't see me with these eyes; I give you supersensuous sight; behold My supreme Yoga power.
NA TU MAM SHAKYASE DRASHTUMANENAIVA SVACAKSHUSHA DIVYAM DADAMI TE CAKSHUH PASHYA ME YOGAMAISHWARAM
Sanjaya (who must have already acquired the "divine eye") describes to Dhritarashtra the mysterious Universal Power of Hari.
There in the body of the God of gods, Arjuna saw the whole universe resting in one, with its manifold divisions. Then, filled with wonder, bending down his head to the Deva in adoration, spoke with joined palms.
I see Thee of boundless form on every side with manifold arms, stomachs, mouths, and eyes; neither the end nor the middle, nor also the beginning of Thee do I see, O Lord of the Universe, O Universal Form.
I see It is a mass of radiance shining everywhere .Having seen Thy immeasurable Form and fearful with many tusks-the worlds are terrified, and so am I. All the creatures (Bhishma, Drona, Sutaputra, all the sons of Dhritarashtra) enter precipitately into Thy mouth, terrible with tusks and fearful to behold. Tell me who Thou art,fierce in form. Have mercy. I desire to know Thee..
Krishna says: "I am the mighty world destroying Time, here made manifest for the purpose of infolding the world. Even without Thee, none of these warriors shall live They have been already slain by me; be thou merely an apparent cause. Conquer the enemies and enjoy the Kingdom."
Sanjaya observes that the trembling Arjuna prostrated himself with joined palms again addresses Krishna.
The Universe is just delighted with Thy glory and rejoices in Thy praise, that Rakshasas fly in fear to all quarters and all the hosts of Siddhas bow down to Thee in adoration. O Great souled One, bow to Thee, greater than, and the Primal Cause of even Brahma,thou art the imperishable, the Being and the non-Being,(as well as) That which is Beyond (them) Thou art the Ancient purusha, the Supreme Refuge of this universe, Thou art the Knower, and the One Thing to be known, Thou art the Supreme Goal. by Thee is the universe pervaded.Thou art Vayu, Yama, Agni, Varuna and the Moon, prajapati and the Great- grandfather Thou art the Father of the world, moving and unmoving; None there exists equal to Thee in the three worlds; Regarding Thee merely as a friend, unconscious of this Thy greatness I addressed Thee as "O Krsna, O Yadava, O friend" please forgive me.Overjoyed am I to have seen what I saw never before, yet mind is distracted with terror. Thee I desire to see as before. Assume that same four-armed form.
The blessed Lord said
Graciously have I shown to thee, this Form supreme, by My own Yoga power, this resplendent, primeval, infinite universal Form of Mine, which hath not been seen before by anyone else. Be not afraid having behold this Form of Mine, so terrific.With gladdened heart, now see again this former Form of Mine.
So, Vasudeva, having thus spoken to arjuna, showed again His own Form.
Having seen this Thy gentle human Form, my thoughts are now composed, and I am restored to my nature.
The blessed Lord said:
Neither by the vedas, nor by austerities, nor by gifts, nor by sacrifice can I be seen as thou hast seen Me. But by single minded devotion I may in this form be known.He who does work for Me alone and has Me for his goal, is devoted to Me, is freed from attachment, and bears enmity towards no creature - he entereth into Me; O Pandava.