Śatapatha Brāhmaṇa ("of a hundred paths") 7.3.1.35

7.3.1.35

sa eṣo 'gnireva vaiśvānaraḥ | etatṣaḍṛcamārambhāyaivemāḥ sikatā nyupyante 'gnimevāsminnetadvaiśvānaraṃ reto bhūtaṃ śiñcati ṣaḍṛcena ṣaḍṛtavaḥ saṃvatsaraḥ saṃvatsaro vaiśvānaraḥ

Now this hymn of six verses is that same Agni Vaisvânara; and it is in order to make a beginning (in the building of the altar) that that sand is scattered,--he thereby pours into it Agni Vaisvânara as seed;--(he does so) with a six-versed hymn: six seasons are a year and the year is Vaisvânara (belonging to all men).