Kṛṣṇa continues with Sāṅkhya, the knowledge of completion:

Just as man casts off his worn-out clothes and puts on new ones, the Self casts off worn-out bodies and enters newer ones, anyāni saṁyāti navāni dehī (2.22).

nainaṁchindantisaśtrāṇi nainaṁdahātipāvakaḥI
na cainaṁ kledayanty āpo na śoṣayati mārutaḥ II 2.23

Weapons do not cleave the Self, fire does not burn It, water does not moisten It, and wind does not dry It. The Self can neither be broken, nor burnt, nor dissolved, nor dried up. It is eternal, all pervading, stable, immovable and ancient.

These verses are amongst the most quoted verses of Bhagavad Gītā. Here, in very few words, Kṛṣṇa expounds upon the entire truth of life and death, mind, body and spirit. He clarifies why we should accept death gladly, as a matter of fact and course, instead of grieving over it. He says this so simply that even an innocent child can understand this truth.

Do we grieve over a dirty shirt that we have cast away when we know we will have a new one? Do we say, ‘Oh, I am so attached to this shirt. I cannot let it go. Let me keep wearing it. I shall be heartbroken if I have to take off this shirt?’ If only we understand that a body needs to be changed when it grows old, in just the same way as the shirt does when it is dirty, there would be no grief, no attachment.

Kṛṣṇa goes on to explain further what that unchanging continuity is. What is the nature of that spirit? How is it that it is everlasting? Kṛṣṇa says, ‘O Arjuna, the Soul is not destroyed at all. No astra, no brahmāstra, no nuclear weapon can destroy the energy within the body. Fire cannot burn It, water cannot wet It, and air cannot dry It. It is not made of the elements and cannot be destroyed by the elements. It is the energy behind the elements that creates the elements. How can It then die?’ ‘It cannot be disintegrated in any manner, by breaking, dissolving, burning or drying, acchedyo ’yam adāhyo ’yam akledyo ’soṣya eva ca. It is eternal. It transcends all the elemental powers. It pervades the Universe, nityaḥ sarva gataḥ sthānuṛ (2.24). It has been there always, sanātanaḥ. Therefore, It never can be destroyed.’

An understanding of the truth that Kṛṣṇa unveils here is the key to immortality. It is the key to liberation from the bondage of life and death. It is the doorway to enlightenment.

‘Do not fear death, nānuśocitum arhasi (2.25).’ Kṛṣṇa says, ‘neither yours nor that of others. It is just a passage. It is the disappearance of this material body. However, you are beyond this material body. Even if the body perishes, you live on, so you do not have to worry or fear.’

What survives death is the sacred spirit in you that can never be destroyed. This spirit is not matter; it is pure energy. How can you destroy energy? Science states that energy can only appear in another form; it cannot be destroyed. As I said before, it is the energy behind the elements; it is that source which creates the elements. It is the energy that has always been and will be, never created, never destroyed. It is unchanging, eternal and all pervading. The experience of every enlightened being verifies the truth that Kṛṣṇa is uttering.

‘When you are that spirit, that energy,’ asks Kṛṣṇa, ‘what is there to grieve about? When you are the Divine yourself, what can you fear? What more can you ask for?’

Listen. At the heart of all torture and killing is fear and greed. When we sincerely contemplate on these teachings, we complete with our fear and greed patterns, and we live peacefully in completion. From this space of completion, comes enriching. Enriching brings the space of Enlightenment in you. The whole cosmos will simply be pouring its energy into you, through you, because you are sharing it with the whole Cosmos!

It is when we are driven by our root patterns that we get fixed in obsessive beliefs and become intolerant of other beliefs, that we become afraid to lose our identity. That insecurity and fear of loss of identity is greater than the fear of death. So we respond violently. To avoid being killed, we kill.

Once we understand what Kṛṣṇa says, that death is like changing a worn-out garment, our fears will disappear. Why do we need that garment at all? We will feel freer, fully liberated when we do not have that garment. Going beyond the garment is going beyond the pattern of body- mind. It is going beyond the root of the root pattern, the cycle of life and death, saṁsāra. It is going to the ultimate liberation, in this life itself. It is the ultimate relaxation.

source: chapter 2, Bhagavadgita Decoded