Bhagavad Gita Verse 20, Chapter 2

na jaayate mriyate vaa kadaachinnaayam bhootvaa bhavitaa vaa na bhooyaha |
ajo nityaha shaashvatoyam puraano na hanyate hanyamaane shareere || 20 ||
 
It (the eternal essence) is neither born, nor does it ever die; nor is it that having come into existence, it will again cease to exist. It is birthless, eternal, changeless and primeval, it is not slain when the body is killed.
 
na : not
jaayate : born
mriyate : dies
vaa : and
kadaachita : ever
na : not
ayam : this
bhootvaa : having come into existence
abhavitaa : ceases to be
vaa na : it is not the case that
bhooyaha : again
ajaha : birthless
nityaha : timeless
shaashvataha : changeless
puraano : primeval
na hanyate : slain
hanyamaane : when slain
shareere : the body
 
This shloka reinforces the attributes of the eternal essence that we have seen so far, that it is eternal and changeless. Any material object, including the human body, goes through six types of modifications: birth, exist, change, grow, decay, and to perish. The eternal essence is beyond all these modifications, hence it is changeless.
 
Two additional qualities of the eternal essence are provided here. The first is that it is birthless. It is logical that it should be birthless, otherwise it could not be eternal and timeless. And since it is birthless, it would have always existed, therefore it is primeval.
 
Note the change in meter to highlight the importance of this shloka.
 
Footnotes
1. "Om namoji aadya" is the very first ovi or stanza of the Jnyaneshwari. Sant Jnyaneshwar invokes the primeval quality of the eternal essence by using the word "aadya" which means primeval.

Bhagavad Gita Verse 19, Chapter 2

ya enam vetti hantaaram yachshainam manyate hatam |
ubhau tau na vijaanito naayam hanti na hanyate || 19 ||
 
A person who believes that it (the eternal essence) slays, and another who believes that it is slain, neither of these understands. It does not slay, nor is it slain.
 
yaha : that person who
enam : this (body dweller)
vetti : believes
hantaaram : slayer
yaha : that
cha : and
enam : this
manyate : believes
hatam: slain
ubhau : both
tau : those
na : do not
vijaanitaha : know
na ayam : this does not
hanti : slay
na hanyate : nor is slain
 
The "It" in this shloka and the following shlokas refers to the body-dweller. Here Shri Krishna addresses another concern that Arjuna had raised. Arjuna thought that that he will be held responsible for killing his kinsmen, which was something that was abhorrent to him. But Shri Krishna through this shloka advised him to use the logic or the perspective of the eternal essence. The eternal essence does not kill, nor does it die from someone else trying to kill it.
 
But how does this apply to us? We are not warriors, and it is rare that we will be put in the position of killing somebody. So there must be another interpretation.This shloka equates the act of slaying to performance of any action, and being slain to any change or modification. In other words, the eternal essence never performs any action, nor does it undergo any change or modification.
 
As an example, let's consider at the sun. Without the sun there will be no activity or life on this planet. There would be no plant life because plants use the sun's energy. There would be no animal or human life because both cannot survive without plants. But, does the sun perform any action pertaining to growing a plant or an animal? Does it get affected by all the changes happening on earth? It does not that that "I caused this forest to grow" or "I was impacted by this eclipse". It remains actionless and changeless.
 
The shloka goes on to say that one who thinks that the eternal essence acts or kills is not using viveka or discrimination, and that person does not have the correct understanding. The person is still thinking at the level of the material object, or in other words, the level of the un-real, and has still not learnt to discriminate between the two.
 
Footnotes
 
1. Verses 19 and 20 are almost verbatim taken from the Katha Upanishad.