This verse was mentioned in today’s Episode 381 – The Mind Fixed Unflinchingly (Teachings of Lord Caitanya, Chapter 1), so as I promised, posting the reference over here:
दिशां त्वमवकाशोऽसि दिश: खं स्फोट आश्रय: ।
नादो वर्णस्त्वम् ॐकार आकृतीनां पृथक्कृति: ॥ ९ ॥
diśāṁ tvam avakāśo ’si
diśaḥ khaṁ sphoṭa āśrayaḥ
nādo varṇas tvam oṁkāra
diśām — of the directions; tvam — You; avakāśaḥ — the power to accommodate; asi — are; diśaḥ — the directions; kham — the ether; sphoṭaḥ — elemental sound; āśrayaḥ — having (ether) as its basis; nādaḥ — sound in its form of unmanifest vibration; varṇaḥ — the primeval syllable; tvam — You; oṁkāraḥ — om; ākṛtīnām — of particular forms; pṛthak–kṛtiḥ — the cause of differentiation (namely, manifest language).
You are the directions and their accommodating capacity, the all-pervading ether and the elemental sound residing within it. You are the primeval, unmanifested form of sound; the first syllable, om; and audible speech, by which sound, as words, acquires particular references.
In accordance with the general process of creation, speech always becomes audible in stages, which proceed from subtle inner impulse to outward expression. These stages are mentioned in the mantras of the Ṛg Veda (1.164.45):
catvāri vāk-parimitā padāni
tāni vidur brāhmaṇā ye manīṣiṇaḥ
guhāyāṁ trīṇi nihitāni neṅgayanti
turīyaṁ vāco manuṣyā vadanti
“Discriminating brāhmaṇas know of four progressive stages of language. Three of these remain hidden within the heart as imperceptible vibrations, while the fourth stage is what people ordinarily understand as speech.”