यदा वा ऋचमाप्नोत्योमित्येवातिस्वरत्येवंसामैवं यजुरेष उ स्वरो यदेतदक्षरमेतदमृतमभयं तत्प्रविश्य देवा अमृता अभया अभवन् ॥ १.४.४ ॥
In plain words
When a man comes to a verse of the Ṛc, he sounds forth Om; and so with the Sāman and the Yajus. This sound is that syllable, and it is the immortal and the fearless. Having entered into it, the gods became immortal and fearless.
The commentators
Chāndogyopaniṣadbhāṣyam
कथ पुन स्वरशब्दवाच्यत्वमक्षरस्येति, उच्यते—
यदा वै ऋचम् आप्रोति ओमित्येवातिस्वरति एव साम एव यजु , एष उ स्वर , कोऽसौ ? यदेतदक्षरम् एतदमृ- तम् अभयम्, तत्प्रविश्य यथागुणमेव अमृता अभयाश्च अभवन् देवा ॥
In plain words
How, then, does this syllable come to be designated by the word 'svara'? The answer is given:
When someone reaches the Ṛc and chants aloud with 'Om'—the Sāman itself, the Yajus, the very tone—what is that tone? It is this imperishable, immortal, fearless syllable. Entering it, the gods became immortal and fearless, each according to their measure.
Close to the Sanskrit
How again is the state of being denoted by the word 'svara' of the syllable? It is said:
When indeed one attains the Ṛc, chanting aloud precisely with 'Om', the Sāman itself, the Yajus, this verily is the tone,—which is that? That which is this imperishable, this immortal, fearless one; having entered that, according to their quality indeed, the gods became immortal and fearless.