Shatapatha Brahmana 11.4.1.10

11.4.1.10

tasmā u haitaduvāca dvāvāghārau pañca prayājā āgneya ājyabhāgo'ṣṭama ete'ṣṭau purastādājyabhāgāḥ saumya ājyabhāgo havirbhāgāṇām prathamo havirhi soma āgneyaḥ puroḍāśo'gnīṣomīya upāṃśuyājo'gnīṣomīyaḥ puroḍāśo'gniḥ sviṣṭakṛdete pañca madhyato havirbhāgāḥ

And he then spoke thus to him:--The two libations of ghee, the five fore-offerings, and, eighth, Agni's butter-portion--these are the eight butter-portions (offered) previously. Soma's butter-portion, being the first of the portions of sacrificial food--for Soma is sacrificial food,---Agni's cake, Agni-Soma's low-voiced offering, Agni-Soma's cake, and (the offering to) Agni Svishtakrit--these are the five portions of sacrificial food in the middle.