CHĀNDOGYA UPANISHAD · 2.23.3

तान्य् अभ्यतपत् ।
तेभ्यो ऽभितप्तेभ्य ओंकारः संप्रास्रवत् ।
तद् यथा शङ्कुना सर्वाणि पर्णानि संतृण्णान्य् एवम् ओंकारेण सर्वा वाक् संतृण्णा ।
ओंकार एवेदं सर्वम् ओंकार एव इदं सर्वम् ॥

tāny abhyatapat ।
tebhyo ’bhitaptebhya oṃkāraḥ saṃprāsravat ।
tad yathā śaṅkunā sarvāṇi parṇāni saṃtṛṇṇāny evam oṃkāreṇa sarvā vāk saṃtṛṇṇā ।
oṃkāra evedaṃ sarvam oṃkāra eva idaṃ sarvam ॥

He brooded on them, and from them, thus brooded on, issued the Om. As all leaves are attached to a stalk, so is all speech (all words) attached to the Om (Brahman). Om is all this, yea, Om is all this.

F. Max Müller · The Upanishads, Sacred Books of the East 1 (1879)