The works of Ādi Śaṅkarācārya

Chāndogyopaniṣadbhāṣyam

Bhashya

Bhashya

अथ यद्वाच स्व प्रपद्ये इति, ऋग्वेदादीन्प्रपद्ये इत्येवतदवोचमिति ।उपरिष्टान्मन्त्रान् जपेत् तत पूर्वोक्तमजरकोश सदिक्वत्स यथावद्व्यात्वा ।द्विर्वचनमादरार्थम् ॥

In plain words

Now, when he said 'I take refuge in svaḥ,' what was spoken was precisely 'I take refuge in the Vedas beginning with the Rigveda.' Having properly meditated upon the previously mentioned ageless sheath, one should subsequently murmur the mantras. The repetition of the words is meant to show deep reverence.

Close to the Sanskrit

Now, what [he] spoke as 'I resort to svaḥ'—precisely that I spoke as 'I resort to the Vedas beginning with the Rigveda'. Afterward, having meditated properly on the aforementioned ageless sheath... one should murmur the mantras. The repetition is for the sake of reverence.