Śatapatha Brāhmaṇa ("of a hundred paths") 5.4.4.24

5.4.4.24

athāhāgnaye sviṣṭakṛte 'nubrūhīti | tadyadantareṇāhutī etatkarma kriyata eṣa vai prajāpatirya eṣa yajñastāyate yasmādimāḥ prajāḥ prajātā etamvevāpyetarhyanu prajāyante tadenam madhyata evaitasya prajāpaterdadhāti madhyataḥ suvati tasmādantareṇāhutī etatkarma kriyata āśrāvyāhāgniṃ sviṣṭakṛtaṃ yajeti vaṣaṭkṛte juhoti

He then says, 'Pronounce the invitatory prayer to Agni Svishtakrit!' And as to why that ceremony is performed between two oblations,--verily, Pragâpati 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;--thus he places him (the Sacrificer) in the very middle of that Pragâpati, and consecrates him in the very middle: that is why that ceremony is performed between two oblations. Having called for the Sraushat, he says, 'Pronounce the offering-formula to Agni Svishtakrit,' and offers as the Vashat is uttered.