The works of Ādi Śaṅkarācārya

Chāndogyopaniṣadbhāṣyam

Verse 43

अथाध्यात्मं वागेवर्क्प्राणः साम तदे-तदेतस्यामृच्यध्यूढं साम तस्मादृच्य-ध्यूढं साम गीयते ।वागेव सा प्राणोऽमस्तत्साम ॥ १ ॥

In plain words

Now regarding the inner embodiment: speech itself is the Ṛk, and breath is the Sāman. That Sāman rests upon this Ṛk. Therefore the Sāman is sung while resting upon the Ṛk. Speech is indeed the Ṛk, and breath is the Sāman; that is the Sāman. 1.

Close to the Sanskrit

Now regarding the self (adhyātma): speech indeed is Ṛk, breath is Sāman. That Sāman is mounted upon this Ṛk. Therefore Sāman is sung while mounted upon Ṛk. Speech indeed is that [Ṛk], breath is that [Sāman]; that is Sāman. 1.