Yoga Sūtra Chapter One verse 27
तस्य वाचकः प्रणवः ॥२७॥
tasya vācakaḥ praṇavaḥ ||27||
Its expression is sacred.
tasya - itsvācaka - expression; verbal , expressed by words; speaking, saying, telling anythinpraṇava - sacred syllableCommentaries and Reflections
Commentary by Paul Harvey:
Its syllables are sacred.