Śatapatha Brāhmaṇa ("of a hundred paths") 1.5.3.5

1.5.3.5

etadvai saṃvatsarasya svam payaḥ | yadājyaṃ tatsvenaivainametatpayasā devāḥ svyakurvata tatho evainameṣa etatsvenaiva payasā svīkurute tasmādājyahaviṣo bhavanti

Now this butter is the year's own liquor: hence the gods gained it (the year) by means of its own liquor; and in the same way he also now gains it by means of its own liquor. This is the reason why clarified butter forms the sacrificial food at these (fore-offerings).