This Self is Brahman — Chandogya Upanishad

The Self,
who can be realized by the pure in heart,
who is life, light, truth, space,
who gives rise to all works,
all desires, all tastes,
who is beyond words,
who is joy abiding —
this is the Self dwelling in my heart.

Smaller than a grain of rice,
smaller than a grain of barley,
smaller than a mustard seed,
smaller than a grain of millet,
smaller even than the kernel of
a grain of millet is the Self.

This is the Self dwelling in my heart,
greater than the earth, greater than the sky,
greater than all the worlds.

This Self,
who gives rise to all works, all desires, all tastes,
who pervades the universe,who is beyond words,
who is joy abiding,
who is ever present in my heart —
This Self is Brahman indeed.

To him I shall attain when my ego dies.

Chandogya Upanishad