Śatapatha Brāhmaṇa ("of a hundred paths") 6.7.1.24

6.7.1.24

tadvā ukheti dve akṣare | dvipādyajamāno yajamāno 'gniryāvānagniryāvatyasya mātrā tāvataivainametadbibharti so eva kumbhī sā sthālī tatṣaṭ ṣaḍṛtavaḥ saṃvatsaraḥ saṃvatsaro 'gniryāvānagniryāvatyasya mātrā tāvattadbhavati

Now 'ukhâ' (consists of) two syllables,--the Sacrificer is two-footed, and the Sacrificer is Agni: as great as Agni is, as great as is his measure, by so much he thus carries him. And that same (pan) is a pot (kumbhî), it is a cauldron (sthâlî); this makes six (syllables),--six seasons are a year, and the year is Agni: as great as Agni is, as great as is his measure, so great does this become.