Śatapatha Brāhmaṇa ("of a hundred paths") 3.6.1.7

3.6.1.7

atha yavamatyaḥ prokṣaṇyo bhavanti | āpo ha vā oṣadhīnāṃ rasastasmādoṣadhayaḥ kevalyaḥ khāditā na dhinvantyoṣadhaya u hāpāṃ rasastasmādāpaḥ pītāḥ kevalyo na dhinvanti yadaivobhayyaḥ saṃsṛṣṭā bhavantyathaiva dhinvanti tarhi hi sarasā bhavanti sarasābhiḥ prokṣāṇīti

Now the sprinkling-water (used on this occasion) contains barley-corns. For the essence (sap) of plants is water; wherefore plants when eaten alone do not satiate; and the essence of water, on the other hand, are the plants; wherefore water when drunk alone does not satiate; but only when the two are united they satiate; for then they are sapful: 'with the sapful I will sprinkle,' so he thinks.