CHĀNDOGYA UPANISHAD · 6.5.3

तेजो ऽशितं त्रेधा विधीयते ।
तस्य यः स्थविष्ठो धातुस् तद् अस्थि भवति ।
यो मध्यमः स मज्जा ।
यो ऽणिष्ठः सा वाक् ॥

tejo ’śitaṃ tredhā vidhīyate ।
tasya yaḥ sthaviṣṭho dhātus tad asthi bhavati ।
yo madhyamaḥ sa majjā ।
yo ’ṇiṣṭhaḥ sā vāk ॥

'Fire (i. e. in oil, butter, &c.) when eaten becomes threefold; its grossest portion becomes bone, its middle portion marrow, its subtilest portion speech.

F. Max Müller · The Upanishads, Sacred Books of the East 1 (1879)