Bhagavan replied: "You want to know how?"

       Bhagavan then quoted in Sanskrit from the Upanishads:

"The mind may be compared to a firestick, the syllable OM to another. Rub the two sticks together by repeating the sacred word and meditating on Brahman, and the flame of knowledge will be kindled in your heart and all impurities will be burnt away." *

                                                                    Kaivalya Upanishad

        "It means that the Self is to be made the lower 'Arani'

(1) and ‘Pranavam’ (Om), the upper Arani and by rubbing them constantly one against the other (2), thus causing by friction, the fire of jnana between the two; the Brahma Jnani burns away the bond known as ignorance. If one understands this and puts it into practice, life’s impurities get destroyed,” said Bhagavan.

The devotee said: “But Bhagavan always tells us that Self-enquiry of ‘Who am I?’ is the most important, is it not?”

Bhagavan replied: “It is the same thing. For enquiry there must be somebody. There is the person and there is  the Self. They are known as the lower Arani and the upper Arani. The enquiry itself is the attrition (3). As one goes on continuously with this attrition the fire called Vijnana gets generated and the bond of ignorance that the Self is different from the object gets burnt out. That means the life’s impurities get destroyed. Then the Self remains as the real ‘Self’. That is ‘Moksha’. It is this, that is called Jnana Yagna or some such thing." So saying Bhagavan assumed silence.  **
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(1)  Arani means a twig of the ‘Sami tree’ used for kindling the sacred fire by rubbing one against another.

(2)  As is stated in all commentaries of the Kaivalya Upanishad, Bhagavan is concurring that the 'rubbing' refers to the process of japa (continuous mental repetition) of the Pranavam (OM) mantra.

(3) Bhagavan's usage of the word 'attrition' directs the devotees to understand that the 'enquiry' is an actual act of sadhana (continuous spiritual practice) , and as Bhagavan often said, a practice that requires patient perseverance over a protracted period of time.
    
     The dictionary definition of 'attrition' is: "A wearing down or away by friction.  A wearing down or weakening of resistance especially as a result of continuous pressure through prolonged physical contact."

* Translation is taken from: The Upanishads - Breath of the Eternal, by Swami Prabhavananda and Frederick Manchester.

** Letters  from  Sri  Ramanasramam, from Suri Nagamma, Sri Ramanashramam 2006, letter of 26th July 1949, page 607.