अथ यदवोचं भूः प्रपद्य इति पृथिवीं प्रपद्येऽन्तरिक्षं प्रपद्ये दिवं प्रपद्य इत्येव तदवोचम् ॥ ३.१५.५ ॥
In plain words
And when I said, "I take refuge in bhūḥ," what I said was: I take refuge in the earth, I take refuge in the middle region, I take refuge in the sky.
The commentators
Chāndogyopaniṣadbhāṣyam· bhāṣya
तथा भू प्रपद्ये इति त्रीँल्लोकान्भूरादीन्प्रपद्ये इति तदवो चम् ॥
In plain words
Similarly, by the phrase 'I take refuge in bhuh,' I expressed: 'I take refuge in the three worlds, beginning with the terrestrial realm.'
Close to the Sanskrit
Likewise, saying 'I take refuge in bhuh', I spoke: 'I take refuge in the three worlds beginning with bhuh.'