Ishavasya Upanishad

Every living being has a Jivatma which is known as the Atman or the Self. The Jivatma which is the life force in all beings, is a part of Paramatma or the one Supreme Brahman. However, there is no difference between Jivatma and Paramatma except for the fact that Jivatma is in a container called body.  
Verse SBG 13:27, “The person who truly sees is the one who sees the Supreme Bhagavan, existing equally, the unperishing within the perishing.” 
Verse SBG 11:33 There, at that time, in one place, Arjuna could see the entire universe with its multifarious divisions all to be united in the body of the Supreme Bhagavan Krishna.
In order to understand what is said above, let us take a pail to the seashore and fill it up with seawater. The water that we have in the pail is in fact a small part of the ocean that we have stored in a container. We don’t call the water in the pail an ocean but we say that it is a pail of water.
When we empty the pail back into the ocean, the water from the pail becomes one with the ocean and it will be impossible to separate the exact portion of water that we had in our pail again. In the brief period during which that small amount of water was in the pail, it had an ‘identity’ of its own and was called a pail of water but when it went back to the ocean, it simply became one with the ocean. The presence of the water in the container gave it that separate identity. 
The container used by the Jivatma is the body, which, unlike the pail we used to carry water, has tools such as the senses and the mind. When a person dies, the Jivatma – (the water in the pail) departs from the body and either enters another container, or in the event it attains Moksha, becomes one with Paramatma – (the ocean). 
Advaita Vedanta is about Universal Oneness and God or the Supreme Brahman referred to in Dharmic scriptures is that one, formless, invisible yet omnipresent, all-pervading and Supreme Force without which no being and nothing can exist. If a being or a thing exists, it must be a part of that complete and perfect whole. It is not easy for humans to contemplate on a Supreme God who is formless.and therefore spiritual seekers may personify or imagine the Supreme Brahman in any form that pleases them and they find easy to relate to. 

SBG 12:05 Those whose minds are set on an unmanifested and impersonal Absolute Power face difficulties in reaching the goal. This is because people always identify with the body and when there is no perceptible form, it is difficult to perceive.

The 18 verses of the Ishavasya Upanishad (Ishavasyopanishad) or Isha Upanishad teach about this Oneness and about the fact that the same Supreme Truth exists in all of us. It is merely the different bodies we occupy that give us separate identities although we are all that one Supreme Energy.

The Ishavaya Upanishad begins with the invocation of the Complete and Supreme Brahman and ends with total surrender before the Ultimate Ishwar, Bhagavan or Krishna.

The Invisible Absolute Brahman is complete and this universe is complete. The visible complete whole comes from the Invisible, Perfect, and Complete Whole. Even when the complete visible whole is removed from the Invisible Complete Whole,  the Absolute Brahman or the Complete Whole remains unchanged. Om, Peace, Peace, Peace.