Śatapatha Brāhmaṇa ("of a hundred paths") 6.2.2.13

6.2.2.13

tadyadvapām purastājjuhoti | ya evāyam purastātprāṇastamasminnetaddadhātyatha yadetena madhyataścaranti madhyato hyayamātmātha yaddhaviṣopariṣṭāccaranti ya evāyamupariṣṭātprāṇastamasminnetaddadhāti śuklavatyo yājyānuvākyāḥ syuḥ śuklarūpāṇāmupāptyai niyutvatyo yadeva niyutvadrūpaṃ tasyopāptyai

Now when in the first place he offers the omentum, he thereby puts into him (Pragâpati) that vital air which is here in front. And when they proceed with that (cake) in the middle, it is because this trunk is in the middle. And when they proceed thereafter with the (meat) oblation, he thereby puts into him that vital air which is behind. The (remaining) offering and invitatory prayers should contain the word 'bright,' with the view of the obtainment of bright forms; and the word 'niyut' (team), for the obtainment of that form which has a team.