Shatapatha Brahmana 5.5.4.34

5.5.4.34

tadu tathā na kuryāt | hvalati vā eṣa yo yajñapathādetyeti vā eṣa yajñapathādya evaṃ karoti tasmādyatraivaiteṣām paśūnāṃ vapābhiḥ pracaranti tadevaitairhavirbhiḥ pracareyurno tarhyāśvinaṃ dvikapālam puroḍāśaṃ nirvapet

Let him, however, not do it in this way; for verily whosoever departs from the path of the sacrifice stumbles, and he who does this indeed departs from the path of the sacrifice. Hence at the very time when they proceed with the omenta of those victims, let them then proceed also with those (three) oblations, and let him not then prepare a two-kapâla cake for the Asvins.