Sankhya Yoga 2.20

 Verse 2.20

न जायते म्रियते वा कदाचि

नायं भूत्वा भविता वा न भूय: |

अजो नित्य: शाश्वतोऽयं पुराणो

न हन्यते हन्यमाने शरीरे || 20||

na jāyate mriyate vā kadāchin

nāyaṁ bhūtvā bhavitā vā na bhūyaḥ

ajo nityaḥ śhāśhvato ’yaṁ purāṇo

na hanyate hanyamāne śharīre

na jāyate—is not born; mriyate—dies; vā—or; kadāchit—at any time; na—not; ayam—this; bhūtvā—having once existed; bhavitā—will be; vā—or; na—not; bhūyaḥ—further; ajaḥ—unborn; nityaḥ—eternal; śhāśhvataḥ—immortal; ayam—this; purāṇaḥ—the ancient; na hanyate—is not destroyed; hanyamāne—is destroyed; śharīre—when the body

The atma is neither born, nor does it ever die; nor having once existed, does it ever cease to be. The atma is without birth, eternal, immortal, and ageless. It is not destroyed when the body is destroyed.

The physical body undergoes six kinds of changes (shat bhava vikara:)

1. Asti - existing (in mother’s womb)

2. Jayate - being born

3. Vartate - growing

4. Viparinamate - changing 

5. Apaksheeyate - weakening

6. Vinashyati -dying 

Atma does not have these six kinds of changes.

Atma is unchanging

In order to establish the fact that atma is unchanging at all times, here is a reference given from sruti.  Verse 20 is in tristup meter while verse 19 is in anushtup meter. The verses of Ramayana and Mahabharata are mainly in anushtup meter which is easier for chanting. 

Krishna says that atma is never born (na jayate) nor will atma ever die (na mriyate). The changes such as birth and death do not belong to atma.

The birth of an object can be of two kinds. One that did not manifest earlier comes into existence ( from abava: to bava:) eg. pot. One that had manifested earlier in a different form transforms into another (from bava: to bava:) eg. a plant growing from a seed. Atma does not have both these changes. 

The next line  nayam bhutva na bhavita va na bhuya: is interpreted in two ways by Shankara. Atma is not something that existed at one point in time and ceases to exist at another ( bhutva buya: na bhavita na). Or atma is not something that was non-existent at one point in time and comes into existence at another ( na bhutva bhuya: bhavita na). Atma was not absent in the past nor will it cease to be in the future.

When something did not exist before and came into existence now it is called the birth of that thing. When something exists for a period of time and ceases to exist at a given point it is called the death of the thing. Since atma does not have these two changes it is never born ( aja:); and eternal ( nitya). There are two kinds of eternity. One is called the pravaha nityam (ever changing but eternal). A river is said to be eternal because it is always there. But the water in the river is constantly flowing. We should not understand atma as pravaha nityam. Hence the word shasvata: removes that doubt. Atma is kutastha nityam ( eternal and unchanging).  Another word that represents atma here is purana. Generally purana means ancient. But here it is given in the sense ever fresh. (pura yeva nava: purana:). Atma is new from the beginning. Also atma is not killed when the body perishes (sharire hanyamane na hanyate). If an object has attributes, then it will be subject to the changes such as growing, waning, shining, shrinking, etc. But atma does not have any attributes, nor divisions, nor limbs. Hence it will never be subject to any change. It is always new and never indulges in any action nor does it allow itself to be an object of the action. So it is akarta and akarmam. Hence it is asochya, a thing that is not worthy of grief.

Shankara concludes his commentary on this sloka by saying that the physical body undergoes six kinds of changes but Krishna establishes that atma does not have these changes.