Śatapatha Brāhmaṇa ("of a hundred paths") 4.3.1.1

4.3.1.1

bhakṣayitvā samupahūtāḥ sma ityuktvottiṣṭhati | puroḍāśabṛgalamādāya tadyatraitadupasanno 'cāvāko 'nvāha tadasmai puroḍāśabṛgalam pāṇāvādadhadāhācāvāka vadasva yatte vādyamityahīyata vā acāvākaḥ

Having drunk (Soma) and said, 'We are invited together,' he (the Adhvaryu) rises. He takes a piece of the cake, and at the place where the Akhâvâka, being seated, is now (about to) recite, he puts the piece of cake in his hand and says, 'O Akhâvâka, say what thou hast to say!' Now, the Akhâvâka was excluded (from the Soma).