अथ यत्प्रथमोदिते स प्रस्तावस्तदस्यमनुष्या अन्वायत्तास्तस्मात्ते प्रस्तुतिका-मा प्रश᳖साकामा प्रस्तावभाजिनो ह्येतस्य साम्न ॥ ३ ॥
In plain words
Now, that part of the chant which corresponds to the first rising of the sun is the prastāva. Human beings are dependent upon it. Therefore, people naturally seek beginnings and praise, because they share in the nature of this prastāva of the sāman.
Close to the Sanskrit
Now that which is at the first rise, that is the prastāva. To that humans are dependent. Therefore they are desirous of commencement and desirous of praise, for they are sharers in the prastāva of this sāman.