Om is everything

वामदेव उवाच |

 

Sage Vamadeva said (to Kartikeya)

 

ओमितीदं सर्वमिति श्रुतिराह सनातनी | 49

 

Om is all this (universe), so said the eternal Shrutis (Vedas).

This repeats in Chapter 16, shloka 52