Patanjali's yoga sutras

तज्जपस्तदर्थभावनम्

tajjapastadarthabhāvanam

Taj = king

Japas = the repetition of a prayer 

Tadartha = has the effect of 

Bhavanam = temple, residence of Isvara 

Praṇavaḥ is a mantra that is an onomatopoeia. Its sound invokes Īśvara’s nature, the ultimate unity that encompasses the indivisible cosmic totality.

Praṇavaḥ is the king of prayers, it turns your body into a temple.