Bhashya
तथा तेजः अशितं तैलघृतादि भक्षितं त्रेधा विधीयते ।तस्य यः स्थविष्ठो धातुः तदस्थि भवति ; यो मध्यमः, स मज्जा अस्थ्यन्तर्गतः स्नेहः ; योऽणिष्ठः सा वाक् ।तैलघृ- तादिभक्षणाद्धि वाग्विषदा भाषणे समर्था भवतीति प्र- सिद्धं लोके ॥
In plain words
In the same way, ingested fire—such as the oils and ghee you eat—divides into three parts. The coarsest part becomes bone. The middle part becomes marrow, the oily substance resting inside the bone. The subtlest part becomes speech. It is a matter of everyday experience that eating oils and similar foods makes the voice clear and capable of fluent speech.
Close to the Sanskrit
Thus, consumed fire, such as oil and ghee eaten, is disposed in three ways. Of that, whichever is the grossest element, that becomes bone; which is the middle, that is marrow, the oil situated inside bone; which is the finest, that is speech. For from the eating of oil and ghee etc., speech becomes clear, capable in speaking, this is well-known in the world.