Shiva Purana
समस्तं व्यस्तमपि च प्रणवार्थं प्रचक्षते ॥ सवार्थवाचकं तस्मादेकं ब्रह्मैतदक्षरम् ॥ ४२ ॥
The whole universe, even if it is disturbed, is called the oṁkāra. Therefore this one syllable Brahman denotes all meanings.
english translation
samastaM vyastamapi ca praNavArthaM pracakSate ॥ savArthavAcakaM tasmAdekaM brahmaitadakSaram ॥ 42 ॥
hk transliteration by Sanscript