Om Mani Padme Hum
Om Mani Padme Hum - the embodiment of compassion in which is felt from within in this mantra. Whilst it has meaning, it is the meaningless and rhythm of the phrase that enables meditation- to clear one's mind and be attuned to that central 'hum' - the sound of the earth.
Kalu Rinpoche, "Through mantra, we no longer cling to the reality of the speech and sound encountered in life, but experience it as essentially empty. Then confusion of the speech aspect of our being is transformed into enlightened awareness."