Śatapatha Brāhmaṇa ("of a hundred paths") 2.4.4.14

2.4.4.14

atha prātaḥ | āgneyaḥ puroḍāśo bhavati maitrāvaruṇī payasyā nedyajñādayānīti nvevāgneyaḥ puroḍāśo 'tha yāmevāmūm maitrāvaruṇīṃ vaśāmanūbandhyāmālabhate saivāsya maitrāvaruṇī payasyā sa paurṇamāsena cāmāvāsyena ceṣṭvā yāvatsaumyenādhvareṇeṣṭvā jayati tāvajjayati tadu khalu mahāyajño bhavati

And on the morrow there are Agni's cake and Mitra and Varuna's curds. Now Agni's cake is (offered) for the sole purpose that it should not forsake the sacrifice and that dish of curds (payasyâ) is to him the same as that barren cow, the anûbandhyâ, which has to be slaughtered for Mitra and Varuna (at the Soma-sacrifice): thus. by performing the full and new-moon offering one gains as much as is gained by performing a Soma-sacrifice; and that (offering) is indeed a great sacrifice.