Śatapatha Brāhmaṇa ("of a hundred paths") 4.2.5.16

4.2.5.16

sa yatpaśumālabhate | rasamevāsminnetaddadhātyatha yatsavanīyaiḥ puroḍāśaiḥ pracarati medhamevāsminnetaddadhāti tatho hāsyaiṣa soma eva bhavati

Now when he slays the victim, he thereby puts flavour into it; and when he proceeds with (the offering of) the Soma feast cakes, he puts sap into it: thus it becomes Soma for him.