Moola Mantra http://www.omoneness.com/moolamantra.html

Hari OM Tat Sat

Hari is one of the names of
the hindu gods. hari is vishnoh.
The word `hari' in itself has another meaning which is far
more beautiful than the word God
whenever a holy name of the supreme lord is uttered we add
OM as a prefix.

Om ity etad brahmano
nedistham nama (Rg Veda) indicates the first goal.

Then tat tvam asi ((Chandogya Upanisad ) indicates the
second goal. which literally means "you are THAT." OR
YOU ARE ONE WITH BRAHMAN.

And sad eva saumya
(Chandogya Upanisad ) indicates the third goal. truth is
beautiful.

combined they become om tat sat.

Bhagavad-gita recommends, therefore, that any work done should be done for
om tat sat, or all fruits of your actions should be
dedicated to HARI, the GOD.

"Hari Om Tat Sat: the divine sound - that is the truth...