Shatapatha Brahmana 9.1.1.43

9.1.1.43

tadāhuḥ | kathamasyaitacatarudriyaṃ saṃvatsaramagnimāpnoti kathaṃ saṃvatsareṇāgninā sampadyata iti ṣaṣṭiśca ha vai trīṇi ca śatānyetacatarudriyamatha triṃśadatha pañcatriṃśattato yāni ṣaṣṭiśca trīṇi ca śatāni tāvanti saṃvatsarasyāhāni tatsaṃvatsarasyāhānyāpnotyatha yāni triṃśattraṃśanmāsasya rātrayastanmāsasya rātrīrāpnoti tadubhayāni saṃvatsarasyāhorātrāṇyāpnotyatha yāni pañcatriṃśatsa trayodaśo māsaḥ sa ātmā triṃśadātmā pratiṣṭhā dve prāṇā dve śira eva pañcatriṃśametāvānvai saṃvatsara evamu hāsyaitacatarudriyaṃ saṃvatsaramagnimāpnotyevaṃ saṃvatsareṇāgninā sampadyata etāvatsa u vai śāṇḍile 'gnau madhyato yajuṣmatya iṣṭakā upadhīyante 'gnayo haite pṛthagyadetā iṣṭakā evamu hāsyaite 'gnayaḥ pṛthakśatarudriyeṇābhihutā bhavanti

As to this they say, 'How does this Satarudriya of his attain to (conformity with) the year, and Agni? how does it correspond to the year, to Agni?' Well, this Satarudriya includes three hundred and sixty (formulas); and (other) thirty, and thirty-five. Now, as to the three hundred and sixty which there are, so many are there days in the year: thereby it obtains the days of the year. And as to the thirty (formulas) which there are, they are the thirty nights of the month: thereby it obtains the nights of the month: thus it obtains both the days and nights of the year. And as to the thirty-five (formulas) there are, they are the thirteenth month, (Agni's) self,--the body (consists of) thirty (limbs), the feet of two, the breath of two (in-breathing and off-breathing), and the head is the thirty-fifth: so much is the year. And in this way this Satarudriya of his attains to (conformity with) the year, Agni, and corresponds to the year, Agni. And, indeed, in the Sândila fire-altar as many bricks with formulas attached to them are placed in the middle, for these bricks are indeed the same as these different Agnis (invoked in the Satarudriya); and thus these Agnis of his come to have oblations offered to them separately by means of the Satarudriya.