Shiva Purana
भूतानामादिभूतत्वाद्भूतादिः कथ्यते तु सः ॥ भूतादेश्शब्दमात्रं स्यात्तत्र चाकाशसंभवः ॥ १७ ॥
Since it is the cause of Bhūtas it is called Bhūtādi. From this is born the Śabdatanmātra, from this the ether.
english translation
bhUtAnAmAdibhUtatvAdbhUtAdiH kathyate tu saH ॥ bhUtAdezzabdamAtraM syAttatra cAkAzasaMbhavaH ॥ 17 ॥
hk transliteration by Sanscript