Shatapatha Brahmana 6.6.1.14

6.6.1.14

pañcādvarasya juhoti | pāṅkto yajño yāvānyajño yāvatyasya mātrā tāvataivainametadreto bhūtaṃ siñcati saptāgneḥ saptacitiko 'gniḥ sapta 'rtavaḥ saṃvatsaraḥ saṃvatsaro 'gniryāvānagniryāvatyasya mātrā tāvataivainametadreto bhūtaṃ siñcati tānyubhayāni dvādaśa sampadyante dvādaśa māsāḥ saṃvatsaraḥ saṃvatsaro 'gniryāvānagniryāvatyasya mātrā tāvattadbhavati

He offers five of the sacrifice,--the sacrifice is fivefold: as great as the sacrifice is, as great as is its measure, by so much he thus pours it forth as seed. Seven (libations) of the fire,--the fire(-altar) consists of seven layers; seven seasons are a year, and Agni is the year: as great as Agni is, as great as is his measure, by so much he thus pours him forth as seed. Those two kinds (of libations) amount to twelve,--twelve months are a year, and Agni is the year: as great as Agni is, as great as is his measure, so great does this become.