Śatapatha Brāhmaṇa ("of a hundred paths") 6.2.2.5

6.2.2.5

ubhayīrgāyatrīśca triṣṭubhaścānvāha | tāsāmukto bandhuruktamvevānvṛcaṃ hiraṇyagarbhavatyāghāramāghārayati prajāpatirvai hiraṇyagarbhaḥ prajāpatiragnirdvādaśāpriyastāsāmukto bandhuruktamvevānvṛca prājāpatyaḥ paśupuroḍāśo ya eva paśorbandhuḥ sa puroḍāśasya dvādaśakapālo dvādaśa māsāḥ saṃvatsaraḥ saṃvatsaraḥ prajāpatiḥ kadvatyo yājyānuvākyāḥ ko hi prajāpatiḥ

He recites both gâyatrî and trishtubh verses: their significance has been told; and (what applies to) the order of the verses has been told. The libation of ghee he makes with the verse containing (the name) Hiranyagarbha; for Hiranyagarbha. is Pragâpati, and Pragâpati is Agni. There are twelve Âprî-verses: their significance has been told; and (what applies to) the order of the verses has been told. The animal cake belongs to Pragâpati, for the relation of the victim is also that of the animal cake. It is one on twelve potsherds: twelve months are a year, and the year is Pragâpati. The offering and invitatory formulas contain the word 'Ka,' for Pragâpati is Ka.