Yoga sutra 1.27
tasya vāchakaḥ praṇavaḥ
The sacred formula: AUM is used to address īśvaraḥ/the Divine
Patanjali introduces mantra yoga in the context of surrender (bhakti yoga). You may speak to īśvaraḥ/the Divine and you may praise īśvaraḥ/the Divine through prayer, chanting or the sound of “AUM” (praṇavaḥ). Aum (ॐ) or Omkar (ओंकार) – “AUM”, is a one-word mantra (chant) which is the most powerful of all mantras.
Damian Cadman-Jones is an authorised teacher of Prana Vashya Yoga™