Bhashya
अथ अनन्तरम् अध्यात्मम् उच्यत ।य एवाय मुख्य प्राणस्तमुद्गीथमुपासीतेत्यादि पूर्ववत् ।तथा ओमिति ह्येष प्राणोऽपि स्वरन्नेति ओमिति ह्यनुज्ञा कुर्वन्निव वागादिप्रवृ- त्त्यर्थमेतीत्यर्थ ।न हि मरणकाले मुमूर्षो समीपस्था प्रा णस्यौकरण शृण्वन्तीति ।एतत्सामान्यादादित्येऽप्योकरणम नुज्ञामात्र द्रष्टव्यम् ॥
In plain words
Now the text turns to the meditation concerning the inner self. As stated before: 'This very principal vital breath is the udgītha; one should meditate upon it as oṃ.' Similarly, the breath moves along uttering oṃ—meaning it functions as though giving its silent consent for speech and the other senses to operate. Since those standing by a dying person do not actually hear a spoken sound of oṃ from the breath, you should understand that the utterance of oṃ in the case of the sun is likewise merely symbolic of granting consent.
Close to the Sanskrit
Now, 'regarding the inner self' is spoken. 'Who is this very principal vital breath, that one should meditate upon as the udgītha' and so forth, as before. Likewise, 'because this prāṇa also, sounding, moves'—meaning, as if giving consent with oṃ for the activity of speech and organs. For those standing nearby at the time of death of a dying person do not hear the utterance of oṃ by the breath. From this similarity, the utterance of oṃ in the sun also should be understood as merely granting consent.