अथ यत्प्रथमोदिते स प्रस्तावस्तदस्य मनुष्या अन्वायत्तास्तस्मात्ते प्रस्तुतिकामाः प्रशंसाकामाः प्रस्तावभाजिनो ह्येतस्य साम्नः ॥ २.९.३ ॥
In plain words
What it is when it has just risen is the prastāva, and upon this men depend; therefore they love praise and love commendation, for they share in the prastāva of this Sāman.
The commentators
Chāndogyopaniṣadbhāṣyam· bhāṣya
अथ यत्प्रथमोदिते सवितृरूपम्, तदस्य आदित्याख्यस्य साम्न स प्रस्ताव , तदस्य मनुष्या अन्वायत्ता पूर्ववत् । त स्मात्ते प्रस्तुतिं प्रशंसां कामयन्ते, यस्मात्प्रस्तावभाजिनो हि एतस्य साम्न ॥
In plain words
Now, the early morning form of the sun is the opening prastāva of this solar sāman, and upon it humanity depends, just as before. Therefore, people seek the opening chant and praise, because they share in the prastāva of this sāman.
Close to the Sanskrit
Now, what is the first-risen form of the sun, that is the prastāva of this sāman named after the sun, upon that humans are dependent as before. Therefore they desire the prastāva and praise, because they are partakers of the prastāva of this sāman.