Jaiminīya (Talavakāra) Brāhmaṇa 1.189

The night is swifter than the day. It has an ehīḷa [cadence] so that there is no falling away. What was left over from the verse and the sāman became the Udveśīya. He who knows this firmly stands with verse and with sāman. One should perform it for a kindly man, not for a cruel man; for the cruel man lives on limited means, while the kindly man lives on what is left over—[this is] only to secure what is left over. Now, raising this sāman as if it were a bamboo pole, the gods advanced against the Asuras. Because they advanced against the Asuras raising it as if to a dwelling (veśam iva), it became the Udveśīya. That is the Udveśīya-nature of the Udveśīya. He who knows this conquers what is to be conquered and does not lose what has been won. This sāman is indeed the form of all the pṛṣṭhas: "The singers of the gāyatra sing of thee" is [the form] of the Gāyatra; "The praisers praise with the hymn" is of the Rathantara; "The priests [sing] to thee, o boy, of hundredfold power" is of the Bṛhat; "Like an entrance, yāyimirāyi" is of the Vairūpa; "I enter," being struck again, is of the Vairāja; "vā yā vu vā u" is of the Mahānāmnīs; "mā irā" is of the Revatīs; "hā i" is of the Vāmadevya. In all this form of the pṛṣṭhas, in the sap, in the fiery energy, in the undefeated meter, he firmly stands at the end of the sacrifice.

Everyone indeed possesses the Ṣoḍaśin.

When the Udveśīya is performed, he repeats the final pāda.

By that form, the Ṣoḍaśin itself is made.

The Ṣoḍaśin is indeed a thunderbolt against the rival.

He hurls this thunderbolt at his hateful rival to strike him down.

Darkness was between the gods and the Asuras.

Those gods in the half-iḷā [...]

saw [it].