Symbol of Iśvara is the Praṇava, which is Oṃ.
Praṇava is a special symbol that specifies the qualities of Iśvara. The sound Oṃ is composite of the letters a + u + m and a fourth element of the peculiar humming of ṃ. Humming of Om is one of the oldest techniques of Yoga and is a gateway to the goals of Yoga. I have blogged about Om here.
tasya – his
vācaka – symbol (from root word ‘to speak; literally ’speaking denoting’)
praṇava – lit. ‘pronouncement’ (from pra + root word ‘to shout exult’)


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