Śatapatha Brāhmaṇa ("of a hundred paths") 4.4.5.1

4.4.5.1

sa vā avabhṛthamabhyavaiti | tadyadavabhṛthamabhyavaiti yo vā asya raso 'bhūdāhutibhyo vā asya tamajījanadathaitacarīraṃ tasminna raso 'sti tanna parāsyaṃ tadapo 'bhyavaharanti raso vā āpastadasminnetaṃ rasaṃ dadhāti tadenametena rasena saṃgamayati tadenamato janayati sa enaṃ jāta eva sañjanayati tadyadapo 'bhyavaharanti tasmādavabhṛthaḥ

He now betakes himself to the expiatory bath (avabhritha). The reason why he betakes himself to the expiatory bath is this. What vital sap there has been in him (Soma and the sacrificer), that (sap) of his he (the priest) has produced (extracted) for the offerings. Now that body (of Soma, i.e. the Soma-husks),--there is no sap in it; (yet) it is not to be cast away: they take it down to the water and--water being sap--he puts that sap into it. Thus he unites him with that sap, and thus he produces him from it,--he (Soma), even when produced, produces him (the sacrificer): and because they take it down (ava-hri) to the water, therefore (the bath is called) avabhritha.