Our bodies go through six transformations – अस्ति (come into existence), जायते (birth), वर्धते (growth), विपरिणमते (Reach maturity, Adulthood), अपक्षीयते (decay) and विनश्यति (death).
But, all these transitions are of the body. We, as Brahman, have nothing to do with it. We are just a witness to these transformations of the body and its activities.
As we saw earlier, this physical body along with Sukshma(सूक्ष्म) and Karan(कारण) Sharir has come into existence due to Prarabdha Karma associated with this life. With the exhaustion of Prarabdha Karma, the physical body will cease to exist. Once that happens, the Sukshma(सूक्ष्म)-Karan(कारण) Sharir will move on to take up the new body.
While exhausting the Prarabdha Karma, new karmas get created. To exhaust that newly created Karma more births are needed. This way, the cycle of life and death called Samsara goes on indefinitely.
As Brahman, the only link we have with Samsara is through consciousness that is felt within. This consciousness happens due to the reflection of Brahman occurring in mind+body.
But, that’s where our relationship with the body ends.
We have nothing to do with the body, its karma, or even with Sukshma and Karan Sharirs and their Sanchit Karmas.
We are eternal, imperishable, free, self-illumined, from which this entire universe has come into existence.
Anyone who has realized this reality or truth of our existence, for them, even though they seem to be fully absorbed in activities of life, nothing is done by them. They go above the laws of Karma, they can neither kill someone nor get killed.
Shri Krishna explains this in the next Shloka:
वेदाविनाशिनं नित्यं य एनमजमव्ययम् |
कथं स पुरुष: पार्थ कं घातयति हन्ति कम् ||2.21||
O’ Parth, how can one who knows the Brahman to be imperishable, eternal, unborn, and immutable kill anyone or can be a reason for anyone’s death.
While we have nothing to do with the body and its activities, body+mind goes through the transformation all the time.
As the physical body ages, it decays and becomes unsuitable for hosting the Suksha and Karan Sharir. Once that happens this body is dropped and Karan Sharir moves on with the new body.
वासांसि जीर्णानि यथा विहाय नवानि गृह्णाति नरोऽपराणि |
तथा शरीराणि विहाय जीर्णा न्यन्यानि संयाति नवानि देही ||2.22||
Just as we throw away worn-out/used clothes and take up new ones, Karan Sharir drops its worn-out body and enters a new one.
Knowing this, we must not grieve for living or dead. These are just nature’s cycles and have nothing to do with us.