Śatapatha Brāhmaṇa ("of a hundred paths") 3.8.3.29

3.8.3.29

sā hovāca | anyatarāmevāhutimahauṣuranyatarām paryaśiṣanniti sa yām paryaśiṃṣaṃstānīmānyavadānāne tato devāḥ sviṣṭakṛte tryaṅgāṇyapābhajaṃstasmāttryaṅgāṇyathāsurā avādyañcīrṣṇoṃ 'sayoranūkasyāparasakthayostasmātteṣāṃ nāvadyedyannveva tvaṣṭānūkamabhyavamattasmādanūkasya nāvadyedathāhāgnīṣomābhyāṃ cāgasya haviṣo 'nubrūhītyāśrāvyāhāgnīṣomābhyāṃ cāgasya haviḥ preṣyeti na prasthitamityāha prasute prasthitamiti

She said, 'Only one oblation have they offered, the other they have left over.' Now that which they left over are these same portions. Thereupon the gods made over three limbs to (Agni) Svishtakrit, whence the Tryaṅga oblations. The Asuras then made portions of the head, the shoulders, the neck, and the hind-thighs: therefore let him not make portions of these. And since Tvashtri spat upon the neck, therefore let him not make a portion of the neck. Thereupon he says (to the Hotri), 'Recite (the invitatory prayer) to Agni and Soma for the havis of the buck!' Having called for the Sraushat, he says (to the Maitrâvaruna), 'Prompt (the Hotri to recite the offering-prayer for) the havis of the buck to Agni and Soma!' He does not say '(the havis) made ready:' when the Soma has been pressed he says 'made ready.'