Bhagavad Gita Verse 13, Chapter 13

sarvatahapaanipaadam tatsarvatokshishiromukham |
sarvatahashrutimalloke sarvamaavritya tishthati || 13 ||
 
With hands and legs everywhere, with eyes, heads and mouths everywhere, with ears everywhere, it is established in all the worlds, pervading all.
 
sarvataha : everywhere
paanipaadam : hands and legs
tat : it
sarvataha : everywhere
akshishiromukham : eyes, heads and mouths
sarvataha : everywhere
shrutimat : eyes
loke : worlds
sarvam : everywhere
aavritya : pervading
tishthati : established
 
How does a child come to learn about electricity? The teacher does not directly tell him that “electricity is defined as a form of energy resulting from the existence of charged particles such as electrons or protons”. The teacher uses what the child already knows and imparts the knowledge to him step by step. So the teacher may first say that to the child: wherever you see bright light in a bulb, that is electricity. Once the child has grasped this concept, then the teacher may say: wherever you see wires connected, that is electricity. Slowly, as the child is able to understand the nuances of atoms and electrons, the teacher then reveals to him the technical definition.
 
Shri Krishna uses a similar process to gently reveal the nature of brahman, the eternal essence, also known as "jnyeyam" or the knowable, to us. Now, it is quite easy for us to see action and sentience - the power to experience things - in living creatures everywhere. So Shri Krishna says that wherever we see action in living beings, symbolically represented by the phrase “hands and legs”, we should recognize the presence of the eternal essence. Furthermore, wherever we see sentience in living beings, symbolically represented by the phrase “eyes, heads, mouths and ears”, we should recognize the presence of the eternal essence.
 
Going back to the example of the child learning electricity, the child may sometimes think that the electricity in a bulb is different than the electricity in a fan, or that the bulb limits the flow of electricity to the fan. To remove any similar misconceptions about the eternal essence, Shri Krishna says that the eternal essence pervades everywhere. In other words, it is only one eternal essence that is functioning through the organs of knowledge and action of all living creatures in all of the worlds, and that one organ does not limit the functioning of the eternal essence in another organ.
 
An example commonly used to illustrate this notion is that of space and pot-space. The space that is in a clay pot and the space outside it is the same. But just because the walls of the pot surround it, we label the space inside as “pot-space”. The pot is a classic example of an upaadhi, something that as though limits the space in it, but does not do so in reality. Space, then, pervades all pots. Similarly, the organs of all living creatures may seem to limit the eternal essence, but not so in reality.
 
Having established the starting point for realizing the eternal essence, Shri Krishna goes one step further in the next shloka.