Jaiminīya (Talavakāra) Brāhmaṇa 17.77

'I myself saw it,' he said. They praised with it. Having praised with it, they discerned the heavenly world. As they were going to the heavenly world, he was left behind. For he spoke an untruth. He became this white-spotted snake (śvitra). These snakes (ahi) are indeed those that are white-spotted. Because he was left behind (ahīyata), that is the snakehood of snakes (ahi). Then others are simply creeping serpents. Therefore, from whomever one might learn, of him one should say: 'From so-and-so I learned.' Moreover, one should desire to speak only truth. This is a sāman that leads to heaven. He reaches the heavenly world who knows thus. 'For you indeed, O divine one...'—there is the word 'you' (tvam), the form of the Bṛhat. This day is connected with the Bṛhat. 'O Pavamāna, most brilliant, [purify] the races...'—saying this, [the verses] contain forms of 'born' (jana-). Thus they generate the Ṣoḍaśin from the third pressing.

Upon them [is sung] the Bṛhatka, one of the Bṛhat [sāmans].

By this, indeed, this day is made connected with the Bṛhat.

The gods, desiring heaven, performed ascetic heat.