Narayana Upanishad is a minor upanishad dedicated to Vishnu worship and it narrates about the importance of chanting Om Narayanaya Namah.
Let ‘OM ’ be first said,
then nama and afterwards Narayanaya.
Let ‘
‘Om ’ is one syllable
‘Nama’ is two syllables and
‘Narayanaya’ five syllables.
Thus ‘Om Narayanaya Nama’ is that eight syllable invocation,
from the repetition of which are obtained:
long life,
wealth,
and progeny;
and finally, immortality, by participating in the bliss
ineffable of god.
The syllable OM is composed
of the letters, ‘a’, ‘u’, and ‘m’, and he who repeats these letters thus joined
together shall be delivered from the miseries of transitory existence.