Jaiminīya (Talavakāra) Brāhmaṇa 1.188

1.188

nārmedhenātirātre'cchāvākāya stuvanti
iḷayā rātrimabhisaṃtanvanti
tadāhuryanti vā ete'nuṣṭubho ya uṣṇikṣvacchāvākasāma kurvantīti
arvāguṣṇiggha khalu vā etāsāmekā madhyoṣṇigekā puroṣṇigekānavadhṛtaṃ
chando'navadhṛtaṃ vāgvadati
vāganuṣṭup
tenānuṣṭubho na yanti
yaitāsāmuttamā sā pratyakṣānuṣṭup
teno vāvānuṣṭubho na yanti
yathā ha vā idaṃ madhukṛtaḥ puṣpāṇāṃ rasānsaṃbharantyevaṃ ha vā etā devatāśchandasāṃ
rasānsamabharan
chandasāṃ hāsya rasena stutaṃ bhavati ya evaṃ veda
ahorātrayorha khalu vā etadrūpaṃ sāma
ṣandrīrṛca āgneyaṃ sāma
ṣandramaharāgneyī rātriḥ
yo ha vā etasmātsāmno'tirātra iyādahorātrayorha vai sa rūpeṇa vivṛhyeta
sa ya enaṃ tatra brūyādahorātrayorenaṃ rūpeṇa vyavṛkṣaditi tathā haiva syāt
tasmādu haitasmātsāmno'tirātre naitavyam

They praise for the acchāvāka priest with the Nārmedha at the Atirātra.
With the Iḷā they connect the night continuously.
Regarding this they say: 'Those who perform the acchāvāka's sāman on the Uṣṇih meters depart from the Anuṣṭubh.'
One of these indeed is an Arvāguṣṇih, one a Madhyoṣṇih, and one a Puroṣṇih; the meter is undefined; speech speaks what is undefined.
Speech is the Anuṣṭubh.
Therefore they do not depart from the Anuṣṭubh.
The one that is the last of them is the direct Anuṣṭubh.
Therefore also they do not depart from the Anuṣṭubh.
Just as the bees collect the saps of flowers, even so these deities collected the saps of the meters.
Praise is sung for him with the sap of the meters, who knows thus.
This sāman is indeed the visible form of day and night.
The verses are addressed to Indra; the sāman is addressed to Agni.
Day belongs to Indra; night belongs to Agni.
Whoever should depart from this sāman at the Atirātra, he would be separated from the visible form of day and night.
Whoever should say of him there: 'He has separated him from the visible form of day and night,' it would indeed be so.
Therefore, one should not depart from this sāman at the Atirātra.