Jaiminīya (Talavakāra) Brāhmaṇa 2-8.368

[Thinking:] '—so that [the Twilight] Sāman may not be left unchanted by us.'
Moreover, the Rathantara is speech; the Āśvina [śastra] is speech; speech is worthy to match speech, [thinking:] 'May this speech match speech!'
And this is the well-known second Twilight Sāman, namely the Jarābodhīya,
so that by that well-known second Twilight Sāman [the rite] may not be left unchanted by us.
Then the Śrudhīya, possessed of renown;
and the two Sāmavṛktis are the two Twilight Sāmans.
In that we have chosen [these] two Twilight Sāmans, [it is with the thought:] 'May the cattle follow into the world of this world-possessing sāman for us!'
Then the Nānada and the Gaurīvita are two world-possessing sāmans, [with the thought:] 'May [cattle] follow into a greater world for us!'
Regarding this they say: 'The Āśvina [śastra] should be recited only three times.' Threefold indeed is speech;
three are these worlds.
If one should recite the Āśvina on every Atirātra, that would be a dispersion of speech.
One should say to the Hotṛ: 'Recite only the Āśvina-rites on the other Atirātras; the Āśvina [proper] is to be recited only three times:
at the beginning, in the middle, and at the end.'
For that indeed is a complete Āśvina which is completed with the Rathantara.
If it should be completed with one, it is the Rathantara at the beginning, in the middle, and at the end; if with two, it is the Rathantara at the beginning, in the middle, and at the end; if with three, it is the Rathantara at the beginning, in the middle, and at the end. It is not completed with four, nor indeed with five.

Now these are the speckled [nights] with a single black one.

These nights are indeed called the 'speckled' [nights].

Among them, a black one also is [included] for pairing, for procreation.

He who knows this is procreated through a pair.

They should perform it either beforehand or afterward.

If they should perform it beforehand, [it is with the thought:] 'Let them have a male leader.'

If afterward, [it is because] the male places the semen in the female from behind, for the deposition of seed.

Prajāpati alone was created here in the beginning, seeing no other, no second [being].

He reflected: 'I indeed was born first; I am the best. Is there indeed another here besides me?'

He looked around.

He saw standing above, beyond himself, another who was greater.

He asked it: 'What are you who are this?'

'I am the brahman,' it said.

He said: 'We two indeed were born first; we are the best. Let us unite; let us be together.'

'No,' it said.

'You are seized by evil.'

'Where is that evil of mine?' [he asked].