Śatapatha Brāhmaṇa ("of a hundred paths") 6.2.2.8

6.2.2.8

tasya saptadaśa sāmidhenyaḥ | saptadaśo vai saṃvatsaro dvādaśa māsāḥ pañca 'rtavaḥ saṃvatsaraḥ prajāpatiḥ prajāpatiragniryāvānagniryāvatyasya mātrā tāvataivainametatsaminddhe

For this (animal sacrifice) there are seventeen kindling-verses; for the year is seventeenfold--there are twelve months and five seasons--Pragâpati is the year, and Pragâpati is Agni: as great as Agni is, as great as is his measure, by so much he thus kindles him.