Śatapatha Brāhmaṇa ("of a hundred paths") 6.2.1.36

6.2.1.36

yadveva vaiśvānaraḥ | ṛtavo haite yadetāścitayo 'gnayo vā ṛtava ṛtavaḥ saṃvatsaraḥ saṃvatsaro vaiśvānaro yadagnaya iti syādati tadrecayeddvādaśakapālo dvādaśa māsāḥ saṃvatsaraḥ saṃvatsaro vaiśvānara āgneyyo yājyānuvākyā agnirūpāṇāmupātyai kāmavatyaḥ kāmānāmupātyai

As to why it belongs to Vaisvânara;--those layers (of the altar) no doubt are the seasons, for the seasons are the fires; and the seasons are the year, and the year is Vaisvânara (belonging to all men). Were it (offered) to Agni (Vaisvânara), he would cause it (the formula) to be redundant. It is one on twelve potsherds: twelve months are a year, and the year is Vaisvânara. The offering and invitatory formulas relate to Agni, for the obtainment of Agni's forms. They contain the word 'kâma' (desire), for the obtainment of his desires.