Shatapatha Brahmana 6.3.1.25

6.3.1.25

tribhiranvicati | trivṛdagniryāvānagniryāvatyasya mātrā tāvataivainametadanvicati pañca sampadā bhavanti pañcacitiko 'gniḥ pañca 'rtavaḥ saṃvatsaraḥ saṃvatsaro 'gniryāvānagniryāvatyasya mātrā tāvattadbhavati

With three he searches,--Agni is threefold: as great as Agni is, as great as is his measure, with so much he thus searches for him. They are five by way of (mystic) correspondence,--Agni (the fire-altar) has five layers; five 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.