Bhagavad Gita Verse 17, Chapter 2

avinaashi tu tadviddhi yena sarvamidam tatam |
vinaashamavyayasyaasya na kashchitkartumarhati || 17 ||
 
But know that (eternal essence) to be indestructible by which all this is pervaded. Nothing ever can destroy that, the imperishable.
 
avinaashi : indestructible
tu : but
tat : that
viddhi : know
yena : which
sarvam : everything
idam : this
tatam : pervades
vinaasham : destruction
avyayasya :  of the imperishable
asya : of this
na : not
kashchit : any
kartum : do
arhati : is able
 
The theme of the ongoing shlokas has been understanding the nature of the eternal essence. This verse gives us two qualities that the eternal essence possesses. Note that the sanskrit word "tat" meaning "that" refers to the eternal essence in this shloka.
 
Firstly, the eternal essence is imperishable. It cannot be destroyed, nor is it created. In the bangle example from the prior verse, the pawn shop owner only cared about the gold content of the bangle and not its shape and form. He could melt that bangle into another ornament, melt it again and make it into another ornament, and so on. In doing so, each subsequent ornament was "created" and "destroyed", but the gold essence was imperishable and indestructible. Similarly, the eternal essence spoken of in these verses is imperishable.
 
Secondly, the eternal essence pervades "all this", which means the eternal essence pervades the entire universe. If we immerse a piece of cloth into water, water pervades each and every fibre of the cloth. There is no part of the cloth that isn't dry. In the same way, from a rock, to plants, to animals, and to humans, the eternal essence pervades everything that is part of the universe.