Bhagavad Gita Verse 20, Chapter 10

ahamaatmaa gudaakesha sarvabhootaashayastithaha |
ahamaadishcha madhyam cha bhootaanaamanta eva cha || 20 ||
 
I am the self, established in the hearts of all beings, O Gudakesha. I am the beginning, middle and also the end of all beings.
 
aham : I
aatmaa : self
gudaakesha : O Gudakesha
sarvabhoota : all beings
aashaya : heart
stithaha : established
aham : I
aadihi : beginning
madhyam : middle
cha : and
bhootaanaam : of the beings
anta : end
eva : also
 
Addressing Arjuna as Gudaakesha, the conqueror of sleep, Shri Krishna begins to describe the 72 expressions of vibhootis of Ishvara from this shloka onwards. He lists the two most important ones first. He says that Ishvara is the self, the “I” that is in the hearts of every being in the universe. Ishvara is also the start, middle and end of all beings in the universe.
 
So what exactly does “self” mean? Let us try to understand its opposite meaning first. When we treat a thing or a person as something different from us, something external to us, then we are creating a subject-object relationship where the subject is our "I" and the object is "him" or "her".
 
For instance, if we take an acquaintance out to dinner, for example, we may ask him to pay his bill separately. There is a sense of separateness between us and the acquaintance. Separating, externalizing, objectifying - all this is the opposite of self-hood.
 
But if we take our spouse or our child to dinner, we don’t even think twice to pay for their dinner. This is because we do not consider a spouse or a child different or external to us. The sense of self-hood is greater here than with a stranger or with an acquaintance. Shri Krishna says that when this sense of selfhood expresses itself in our hearts, we should know that it is Ishvara’s primary expression. If we can remember this constantly, if we can treat everything and every one as no different than ourselves, we do not have to remember any other expression of Ishvara. We are done.
 
So what is the practical implication of understanding Ishvara in this manner? Our sense of I-ness and my-ness automatically drops. There will be nothing in us that asserts “my will”, “my plan”, “my thinking”, “I am going to do this” and so on. It will all become Ishvara’s will, Ishvara’s plan, Ishvara’s thinking, Ishvara’s doing. All worries and anxieties will disappear because the “I” who worries is no longer present.
 
If we are not able to comprehend Ishvara as our own self, then Shri Krishna provides another expression of Ishvara. He says that we should think of Ishvara as the one who creates, sustains and dissolves all the names and forms in the universe, just like the ocean creates, sustains and dissolves all waves. If we can think in this manner, Ishvara becomes all-pervading, ever present at all times.
 
Now, thinking Ishvara as the self, or as the beginning, middle and end of all beings, is difficult when we are beginners. For most of us, it is easier to see Ishvara in tangible people and objects. We will see those types of expressions in the following shlokas.