AUM is the Self indeed.

OM! This syllable is this whole world.
Its further explanation is:
the past, the present, the future
everything is just the word OM.
And what-ever else that transcends threefold time
that, too, is just the word OM.

For truly everything here is Brahman;
this Self (Atman) is Brahman.
This same Self has four fourths:
the waking state, outwardly cognitive...
the dreaming state, inwardly cognitive...
the deep sleep state, unified, a cognition-mass...
and the state of being one with the Self,
the cessation of phenomena, tranquil....

This is the Self with regard to the word OM,
with regard to its elements.
The elements are the fourths, the elements:
the letter A, the letter U,the letter M.

The waking state, the common-to-all-men, is the letter A...
the sleeping state, the Brilliant, is the letter U...
the deep-sleep state, the Cognitional, is the letter M...
The fourth is without an element,
with which there can be no dealing,
the cessation of phenomena, benign, without a second.

This AUM is the Self indeed.

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from the  Upanishads

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