The knowledge of the Holy Gita was spoken at the time when the Mahabharata war was about to begin. Arjun had refused to fight. Why was the war happening? This conflict cannot even be termed a "Righteous War" (Dharmayuddha) because it was a matter of property distribution between two families. The property division between the Kauravas and the Pandavas was not being resolved. The Kauravas had refused to give even half the kingdom to the Pandavas.
To mediate between the two sides, Lord Shri Krishna went as a messenger of peace three times. However, both sides remained adamant in their respective stubbornness. Shri Krishna also warned them of the destruction caused by war, saying, "Who knows how many sisters will be widowed? Who knows how many children will be orphaned? Nothing but a great sin will be gained. In war, who knows who will die and who will survive?"
The third time Shri Krishna went to negotiate a compromise, both sides showed him the lists of kings and their respective armies supporting them, stating, "This many kings are on our side, and this many are on ours." When Shri Krishna saw that neither side was budging and both were fully prepared for war, he thought, "There is one more move; let me try that today as well."
Shri Krishna thought that perhaps the Pandavas, being his relatives, were not giving up their stubbornness because they felt that since Shri Krishna was with them, victory was certain (as Shri Krishna's sister, Subhadra Ji, was married to Shri Arjun Ji). Shri Krishna declared, "On one side will be my entire army, and on the other side will be me alone; furthermore, I pledge that I will not even lift a weapon."
This announcement caused the ground to slip from beneath the Pandavas' feet. They felt that their defeat was now certain. With this thought, the five Pandavas left the assembly, saying they needed to deliberate. After some time, they requested Shri Krishna to come out of the assembly. When Shri Krishna came out, the Pandavas said, "O Lord! Just get us five villages. We do not want war. Our honor will be preserved, and your wish that there be no war will also be fulfilled." Having shared their opinion with Shri Krishna, they returned to their home.
Shri Krishna was very pleased with the Pandavas' decision and thought that the bad times had passed. He returned to the assembly, where only the Kauravas and their supporters remained. Shri Krishna said, "Duryodhan, the war has been averted. This was my heartfelt wish as well. Just give the Pandavas five villages; they say they do not want war."
Duryodhan replied, "There is not even a needlepoint’s worth of land for the Pandavas. If they want a kingdom, let them come to the battlefield of Kurukshetra for war." Angered by this, Shri Krishna said, "Duryodhan, you are not a human, but a demon. What a difference between half a kingdom and five villages! Listen to me and grant them five villages."
Incensed by Shri Krishna's words, Duryodhan ordered the warriors present in the assembly to seize Shri Krishna and throw him into prison. Upon receiving the order, the warriors surrounded Shri Krishna from all sides. Shri Krishna then displayed his Virat Roop (Gargantuan/Universal Form). Consequently, all the warriors and Kauravas hid under their chairs in fear, and their eyes were forced shut by the intense radiance of his body. Krishna then left the place.
Consider this: The evidence of displaying the aforementioned Virat Roop is clearly present in the Brief Mahabharata published by Gita Press Gorakhpur.
Evidence: "The Knowledge of the Gita was not Spoken by Shri Krishna":
When the knowledge of the Holy Gita was being imparted on the battlefield of Kurukshetra, in Chapter 11, Verse 32, the Lord speaking the Gita says, "Arjun, I am an enlarged Kaal (Time/Destruction). I have now appeared to devour all the worlds." Just think—Shri Krishna was already with Shri Arjun. If Shri Krishna were speaking the knowledge of the Holy Gita, he would not have said, "I have now appeared."
Furthermore, in Chapter 11, Verses 21 and 46, Arjun says, "O Lord! You are devouring even the sages, gods, and perfected beings (Siddhas), who are singing your praises by chanting Vedic mantras and wishing for the protection of their lives. Some are hanging in your teeth, and some are entering your mouth. O Sahastra-bahu (Thousand-armed Lord)! Please return to your four-armed form. I cannot maintain my composure seeing this terrifying form."
From the details above, two facts are established:
In Gita Chapter 4, Verse 9, it is said, "O Arjun! My birth and actions are divine." The meaning is that Kaal Brahm performs actions by entering the bodies of others. For example, Shri Krishna had pledged that he would not lift a weapon to kill anyone in the Mahabharata war. Yet, Kaal Brahm entered Shri Krishna, picked up a chariot wheel, and killed many soldiers. The sin was attributed to Shri Krishna, and his pledge was broken, tainting his reputation.
At the moment Kaal Brahm projected his Virat Roop outside of Shri Krishna's body, it was so radiant that Arjun became terrified, and Shri Krishna was overshadowed by the brilliance of that gargantuan form. That is why Arjun asked, "Who are you?" Would someone ask their brother-in-law, "Who are you?" Therefore, the knowledge of the Gita was spoken by Kaal Brahm after entering Shri Krishna's body.
Conclusion: The Giver of the Gita is not Shri Krishna, because Shri Krishna was visibly present before everyone. Shri Krishna does not say, "I remain hidden by my Yogmaya." Thus, the knowledge of the Gita was spoken by Kaal, who entered Shri Krishna like a ghost.