Shiva Purana
तस्माद्वेदादिरेवाहं प्रणवो मम वाचकः॥ वाचकत्वान्ममैषोऽपि वेदादिरिति कथ्यते ॥ २०॥
I am the source of the Vedas. Praṇava expresses me. Since it expresses me the Praṇava too is mentioned as Vedādi.
english translation
tasmAdvedAdirevAhaM praNavo mama vAcakaH॥ vAcakatvAnmamaiSo'pi vedAdiriti kathyate ॥ 20॥
hk transliteration by Sanscript