Jaiminīya (Talavakāra) Brāhmaṇa 2-2.7

They indeed go, but just as one would go without food, so is it.
Now as to why they are Ukthyas:
Ukthas are cattle;
cattle are food.
Just as one would approach a superior who rejoices with food, in the very same way they approach this [day] with the Ukthya Svarasāman [days].
Moreover, these two—the Viśvajit and the Abhijit—are of the nature of the deities;
the Svarasāman days are food.
Just as one, having placed food on a platter, would bring it to a superior, even so one brings this food to him, namely the Viśvajit and Abhijit.
Moreover, a pacification is thereby performed.
There would be the Agniṣṭoma-sāman, the Āgnimāruta recitation, [and] the Viṣuvant.
Who could approach these three fires flaming on both sides? One would surely lie scorched.
Therefore, they are interspersed with Ukthas.
Ukthas are cattle;
cattle are food.
With food they pacified him;
having pacified him with the Nārmedha [sāman], they finally approach him.

These indeed are the Viśvajit and the Abhijit.

The one amounts to eight Virājs of thirty-six syllables, the other to eight.

This world is the Abhijit; that [world] is the Viśvajit.

The Svarasāman days are cattle.

In that they chant with the Svarasāman days after chanting with the Abhijit, in this world indeed

they establish cattle.

And in that they chant with the Viśvajit after chanting with the Svarasāman days, therefore cattle live

from the gift from yonder [world].

Of that Viṣuvant day there are ten twenty-five-fold chants and two

stotriya verses.