Shatapatha Brahmana 11.1.6.13

11.1.6.13

sa aikṣata prajāpatiḥ imaṃ vā ātmanaḥ pratimāmasṛkṣi yatsaṃvatsaramiti tasmādāhuḥ prajāpatiḥ saṃvatsara ityātmano hyetam pratimāmasṛjata yadveva caturakṣaraḥ saṃvatsaraśca!turakṣaraḥ prajāpatisteno haivāsyaiṣa pratimā

Pragâpati bethought himself, 'Verily, I have created here a counterpart of myself, to wit, the year;' whence they say, 'Pragâpati is the year;' for he created it to be a counterpart of himself: inasmuch as 'samvatsara (year),' as well as 'Pragâpati,' consists of four syllables, thereby it (the year) is a counterpart of him.