Kṛṣṇa starts His message as a response to Arjuna’s question. This shows that Arjuna still needs to have the maturity. He asks, ‘The Sun god is elder to you by birth; he is so much your senior. How am I to understand that in the beginning you instructed this science to him?’

Arjuna and Kṛṣṇa are almost of the same age. Suddenly, Kṛṣṇa says He gave this science to the Sun god thousands of years ago! Moreover, Arjuna lived with Kṛṣṇa for a long time. He knows and has seen the human side of Kṛṣṇa, all of Kṛṣṇa’s līlā (plays), all of Kṛṣṇa’s moods. So now, it is very difficult for Arjuna to believe Kṛṣṇa’s words.

When Rāmakṛṣṇa declared that the same being who came as Rāma and Kṛṣṇa had now come down in the form of Rāmakṛṣṇa, he was called mad! People did not receive or respect him. But a few qualified people received his words and transformed their lives.

This is what all disciples who live around Enlightened Masters undergo. They find it difficult to understand the Divine descending and walking on the planet Earth in human form. Arjuna struggles to understand. How can the Divine descend? Arjuna is shocked when Kṛṣṇa says, ‘Thousands of years ago, I taught this science of Enlightenment to the Sun God, Vivaṣvān.’

For example, suddenly if I tell you, ‘A hundred years ago, I was the person who taught all these sciences to some enlightened Master!’ How will you feel?‘ Naturally questions will arise. Here the same thing happens. Arjuna thinks, ‘How can I understand?’ He has become a little polite and intelligent. In the second chapter, when Kṛṣṇa says, ‘Arjuna, go and fight,’ Arjuna asks, ‘How can you say this? How can you tell me to sin?’ Now he says, ‘How can I understand? Please tell me.’ He does not say, ‘How can you say this?’’ He is now ready to believe, but he wants a little explanation.

Whenever enlightened Masters descend on the planet Earth, they face this trouble, again and again. When Rāmakṛṣṇa declared that the same being who came as Rāma and Kṛṣṇa had now come down in the form of Rāmakṛṣṇa, he was called mad! People did not receive or respect him. But a few qualified people received his words and transformed their lives.

See, all movements can be started in two ways.

One is the political movement which starts with huge numbers of followers. The bigger the crowd, the more powerful he feels. He makes all kinds of claims. These movements, over a period of time, slowly dwindle in quality and quantity. Once the founder dies, the movement dies.

The second type of movement is the spiritual mission. When the Masters declare the truth, the quantity may not be there, but the quality will be there. When Rāmakṛṣṇa made this declaration, hardly sixteen disciples were ready to trust Him. These few transformed their lives. It started as a very slow, small movement but expanded into an international mission. Today, millions worship him as God. These spiritual missions start in a very small way but expand and explode.

For a political person, the inspiration is in numbers. How well is it covered in media? It matters to him how many newspaper cuttings he can collect. But for a spiritual person what matters is how many ego-cuttings he can do and liberate? For a political person it is the paper cutting, for a spiritual person, it is the ego-cutting.

I always tell people, my best discourses are always given to small, close devotees. Because when you speak the truth to an intimate group, it will be straight. It will shake your whole being and transform your whole life. Those who are not yet ready cannot receive it. For a spiritual discourse, what matters is the quality of the people present.

This very Gītā is delivered to only one person. When Kṛṣṇa delivered Gītā, only one person listened to it. But today, millions and millions, not even millions, billions read and practice it. For a billion Hindus, this is the basic scripture. Only one person listened to Kṛṣṇa. Today the whole world uses it. To express the truth, the quality of the person who listens is important, not the quantity of persons. Now Kṛṣṇa starts to answer this question. Let me repeat this beautiful verse:

śrī bhagavān uvāca

bahūni me vyatītāni janmāni tava cārjuna I
tāny ahaṁ veda sarvaṅi na tvaṁ vettha parantapa II 4.5

Bhagavān says, ‘O Arjuna, many, many births both you and I have passed. I can remember all of them but you can’t.’ Then He says, ‘Although I am unborn, imperishable and the Lord of all living entities, I reappear by my original māyā, by controlling my nature.’

ajo’pi sann avyayātmā bhūtānām īsvaro’pi san I

prakṛtiṁ svām adhiṣṭhāya sambhavāmy ātma-māyayā II 4.6

I think this is the first time He declares His divinity! All this while, Kṛṣṇa was only playing the role of ācārya (teacher,) intellectually enriching Arjuna of the truth and giving him knowledge. For the first time, He opens up. He declares the truth about His nature. He shows the divinity of His nature. I think this is the point where Kṛṣṇa starts to speak the ultimate truth as it is. Till then, I think He was a little shy to open up to Arjuna!

When a disciple is not ready, you can’t open up, you can’t tell the truth. Now, the disciple is ready. So Kṛṣṇa opens up. He says, although I am unborn and my transcendental body never deteriorates and although I am the Lord of all living entities, I still appear in every millennium in my original transcendental form.

Three things we need to understand here. First He says, ‘I am unborn, ajopi. I never take birth. I am the ultimate Parabrahma. I am the ultimate energy.’ I don’t think anyone else has declared it so clearly. Here, Kṛṣṇa straightaway declares the truth. ‘I am God, bhūtānām īsvaro’pi san,’ He says.

Please listen, when the disciple is mature, the Master is understood. Here, straightaway Kṛṣṇa declares, ‘I am unborn, ajopi, I am unborn, eternal consciousness, and my transcendental body never deteriorates, avyayātmā. You can always relate with me. I am unborn and I never die.’

Understand, that which never takes birth can never die; only that which takes birth can die. Here Kṛṣṇa declares, I never take birth and I never die. I am the Lord of all living entities – ajo’pi sann avyayātmā bhūtānām īsvaro’pi san.

source: chapter 2, Bhagavadgita Decoded verses, 4.4 – 4.8