Shatapatha Brahmana 9.1.1.16

9.1.1.16

caturdaśaitāni yajūṃṣi bhavanti | trayodaśa māsāḥ saṃvatsaraḥ prajāpatiścaturdaśaḥ prajāpatiragniryāvānagniryāvatyasya mātrā tāvataivainametadannena prīṇāti namo nama iti yajño vai namo yajñenaivainametannamaskāreṇa namasyati tasmādu ha nāyajñiyam brūyānnamasta iti yathā hainam brūyādyajñasta iti tādṛktat

There are here fourteen formulas,--thirteen months are a year, and Pragâpati is the fourteenth; and Pragâpati is Agni: as great as Agni is as great as is his measure, with so much food he thus gratifies him. 'Reverence! reverence!' he says;--reverence being sacrifice, it is by sacrifice, by reverence, that he thus reveres him. Therefore he must not mention any one unworthy of sacrifice, for it would be just as if he were to say to him, 'Sacrifice be to thee!'