Bhashya
ग्वक्तव्येत्यारम्भः—यः कश्चित् लोके शब्दो ध्वनिः ताल्वा-दिव्यङ्ग्यः प्राणिभिः वर्णादिलक्षणः इतरो वा वादित्रमेघा-दिनिमित्तः सर्वो ध्वनिः वागेव सा ।इदं तावद्वाचः स्वरू-पमुक्तम् ।अथ तस्याः कार्यमुच्यते—एषा वाक् हि यस्मात्अन्तम् अभिधेयावसानम् अभिधेयनिर्णयम् आयत्ता अनु-गता ।एषा पुनः स्वयं नाभिधेयवत् प्रकाश्या अभिधेयप्र-काशिकैव प्रकाशात्मकत्वात् प्रदीपादिवत् ; न हि प्रदीपादि-प्रकाशः प्रकाशान्तरेण प्रकाश्यते ; तद्वत् वाक् प्रकाशिकैवस्वयं न प्रकाश्या—इति अनवस्थां श्रुतिः परिहरति—एषा हि न प्रकाश्या, प्रकाशकत्वमेव वाचः कार्यमित्यर्थः ॥
In plain words
Every sound that exists in the world—whether articulated by human organs as letters or produced externally by drums and clouds—is speech itself. We have described the nature of speech; now we examine its function. Speech is that upon which all expression converges and is resolved. Yet speech is not an object to be revealed by something else; like a lamp, it is self-luminous and reveals everything else. Just as a lamp's light is never illuminated by another light, speech reveals without needing to be revealed by another. By establishing this, scripture avoids an endless regress: speech is never to be illuminated, for its very nature is to illuminate.
Close to the Sanskrit
The introduction on speech: whatever sound exists in the world, produced by palate etc., characterized by letters or other, caused by instruments or clouds, all such sound is speech itself. This much of the nature of speech has been stated. Now its function is stated: this speech indeed is dependent upon that where the object of expression ends and is determined. This again is not to be illuminated like an object, but is itself the illuminator of objects because of its luminous nature, like a lamp; for the light of a lamp etc. is not illuminated by another light; similarly speech is an illuminator itself and is not to be illuminated—thus scripture avoids infinite regress: this indeed is not to be illuminated; the meaning is that being an illuminator alone is the function of speech.