Śatapatha Brāhmaṇa ("of a hundred paths") 5.2.2.18

5.2.2.18

athāhāgnaye sviṣṭakṛte 'nubrūhīti | tadyadantareṇāhutī etatkarma kriyata eṣa vai prajāpatirya eṣa yajñastāyate yasmādimāḥ prajāḥ prajātā etamvevāpyetarhyanu prajāyante tanmadhyata evaitatprajāpatimujjayati tasmādantareṇāhutī etatkarma kriyata āśrāvyāhāgniṃ sviṣṭakṛtaṃ yajeti vaṣaṭkṛte juhoti

Thereupon he says, 'Recite (the invitatory formula) to Agni Svishtakrit!' Now, as to why this rite is performed between two oblations. Pragâpati, truly, is that sacrifice which is here performed, and from which these creatures have been produced,--and, indeed, they are even now produced after this one: he thus wins Pragâpati in the very middle: therefore that rite is performed between two oblations. Having made (the Âgnîdhra) utter the Sraushat, he says, 'Pronounce the offering-prayer to Agni Svishtakrit!' and offers as the Vashat is uttered.