तस्यै वाचः पृथिवी शरीरम् ।ज्योतीरूपमयमग्निः ।तद्यावत्येव वाक्तावती पृथिवी तावानयमग्निः ॥बृह. १,५.११ ॥
In plain words
Of that speech the earth is the body, and this fire is its form of light. Therefore, as far as speech reaches, so far reaches the earth and so far this fire.
The commentators
Bṛhadāraṇyakopaniṣadbhāṣyam· avatāraṇikā
व्याख्यातो वाङ्मनःप्राणानामाधिभौतिको विस्तारः ; अथायमाधिदैविकार्थ आरम्भः—
In plain words
The material exposition concerning speech, mind, and prāṇa has now been completed; we now begin their exposition in relation to the cosmic deities.
Close to the Sanskrit
The physical expansion of speech, mind, and prāṇas has been explained; now begins the subject matter pertaining to the cosmic deities.