Ajapa Japa — The Unspoken Mantra of the Self
The natural mantra So'Ham (I am That) that arises with every breath — 21,600 times daily — is the Advaita recognition that the individual self is constantly, unconsciously affirming its identity with Brahman.
Ajapa Japa (the mantra that is not recited — from a = not, japa = recitation) refers to the natural mantra So'Ham (So = That/Brahman, Ham = I am) that arises with every breath — inhalation as 'So' (That), exhalation as 'Ham' (I am). This means every breath is an unconscious repetition of the Mahavakya 'Aham Brahmasmi' (I am Brahman). The individual soul constantly, unconsciously, declares its identity with the ultimate reality — 21,600 times per day with each breath cycle. Advaita practice makes this unconscious process conscious: by bringing awareness to the natural So'Ham vibration in the breath, the practitioner transforms ordinary breathing into continuous meditation on the identity of Atman and Brahman. The Yoga Vasistha and Shiva Samhita both describe So'Ham as the most powerful mantra — not because it is assigned by a teacher but because it is the natural vibration of existence itself.
With each breath, the Self proclaims its own nature: So'Ham — I am That.
In the tradition this is the Ajapa Japa — the 'unspoken repetition' of Hamsa / So'Ham said to sound of itself in the natural rhythm of inhalation and exhalation, so that the breath is treated as a mantra one need not consciously recite; it is expounded in texts such as the Hamsa Upanishad.
Yoga Vasistha