Śatapatha Brāhmaṇa ("of a hundred paths") 3.2.3.10

3.2.3.10

athaibhyaḥ somaḥ prārocata | tamayajantsa yatsaumyaṃ yajñasyāsīttadapaśyanyadvā ārdraṃ yajñasya tatsaumyaṃ tadapaśyaṃstadatanvata

Then Soma appeared to them: they offered to him; whereby they perceived that part of the sacrifice which was of Soma's nature. Now of Soma's nature is what is moist in the sacrifice: that they thereby perceived and spread.