Śatapatha Brāhmaṇa ("of a hundred paths") 2.4.4.18

2.4.4.18

atha prātaḥ | āgneyaḥ puroḍāśo bhavati maitrāvaruṇī payasyā nedyajñādayānīti nvevāgneyaḥ puroḍāśo 'thaitāvevārdhamāsau mitrāvaruṇau ya evāpūryate sa varuṇau yo 'pakṣīyate sa mitrastāvetāṃ rātrimubhau samāgacatastadubhāvevaitatsaha santau prīṇāti sarvaṃ ha vā asya prītam bhavati sarvamāptaṃ ya evametadveda

And on the morrow there is Agni's cake and Mitra and Varuna's curds. Now Agni's cake is (offered) for the sole purpose that it may not forsake the sacrifice. Mitra and Varuna, on the other hand, are the two half-moons: the waxing one is Varuna, and the waning one is Mitra. During that night (of new moon) these two meet, and when they are thus together he pleases them with that (cake-offering): and, verily, all is pleased with him, all is obtained by him who thus knows this.