Bhashya
सत्यकाम परं चापरं च यदोंकारः' 'ओमित्यात्मानं युञ्जीत' 'ओमिति ब्रह्म' 'ओंकार एवेदं सर्वम्' इत्यादिश्रुतिभ्यो रज्ज्वादिरिव सर्पादिविकल्पस्य अद्वयात्मा परमार्थः सन् प्राणादिविकल्पास्पदो यथा, तथा सर्वो वाक्प्रपञ्चः प्राणाद्यात्मविषयः ओंकार एव ।स च आनुष्टुबङ्गं सत्त्वात्मस्वरूपमेव, तदभिधायकत्वात् ।ओंकारविकारशब्दाभिधेयश्च सर्वः प्राणादिः आत्मविकल्पः अभिधानव्यतिरेकेण नास्ति, 'वाचारम्भणं विकारो नामधेयम्' 'तस्येदं वाचा तन्त्या नामभिर्दामभिः सर्व सितम्' 'सर्व हीदं नामनि' इत्यादि- श्रुतिभ्यः ।
In plain words
Satyakāma, Om is both the highest reality and the nearest one — the scriptures themselves say so: unite your very self with Om; Om is Brahman; Om alone is all of this. Picture a rope mistaken for a snake in the dark. The rope never stops being a rope, and yet every fear the mind invents hangs from it. In just the same way, the one undivided Self — reality itself — is what every play of breath, every guise the self seems to wear, quietly rests upon. And the whole world spoken into being through language, every name given to breath or to self, is nothing but Om. Om carries the Anuṣṭubh metre as its own limb, because that metre is simply Om's voice, the very sound of being itself. And whatever we call a 'modification' of Om — every breath, every apparent shape the self takes — has no life of its own apart from being named. The scriptures say it plainly: a thing that seems to change is only ever a name, a handle language hands us; with speech, as with a cord, everything here is tied down by names as if by ropes; all of this, truly, lives only in its name.
Close to the Sanskrit
O Satyakāma, since Om is both the higher and the lower [Brahman] — as such śruti-passages say: 'let one yoke the self to Om', 'Om is Brahman', 'Om alone is all this' — [the matter stands thus]: just as the non-dual Self, though the ultimate reality, is the seat of the differentiated notions of prāṇa etc., the way a rope is the seat of the differentiated notion of a snake etc. [superimposed on it], so too the entire expanse of speech, whose object is the self under the guise of prāṇa etc., is Om alone. And that [Om], having the Ānuṣṭubh metre as its limb, is precisely the very nature of the self as pure being, because it is the expresser of that. And whatever is denoted by the phrase 'a modification of the word Om' — every prāṇa etc., every differentiated notion of the self — does not exist apart from its verbal designation: from such śruti-passages as 'a modification is a mere name, a handle for speech', 'by speech, as by a cord, all this is bound here with names as with ropes', 'all this indeed rests in name'.