Jaiminīya (Talavakāra) Brāhmaṇa 10.38

The word “vī” is the characteristic of the atmosphere; this day belongs to the atmosphere. “For with Indra you will see each other” — [this] belongs to Indra. The words “sam” and “vi” are the characteristic of the atmosphere: upward from here is this world, and yonder [world is] turned hither from over there. And this atmosphere is “sam” and “vi”. “Coming together with the fearless, gladdening, of equal splendor” — the third and fourth days are indeed equal. From the third day, the fourth day was born. “Thereafter according to their own nature they again set into motion the state of an embryo” — thus they again set into motion the state of an embryo on the third day for the birth of the fourth day. “Assuming a sacrificial name / with those who shatter even the firm [stronghold], with the draft-horses, O Indra, even into the hiding-place / you found the cows” — [these verses] contain [the word] “cow” and contain cattle, for the securing of cattle; for this day is cattle.

“I call upon the two to whom belongs this” —

thus [begins the hymn] belonging to Indrāgnī.