Śatapatha Brāhmaṇa ("of a hundred paths") 2.6.2.19

2.6.2.19

atha keśaśmaśrūptvā | samārohyāgnā udavasāyeva hyetena yajate na hi tadavakalpate yaduttaravedāvagnihotraṃ juhuyāttasmādudavasyati gṛhānitvā nirmathyāgnī paurṇamāsena yajata utsannayajña iva vā eṣa yaccāturmāsyānyathaiṣa kLptaḥ pratiṣṭhito yajño yatpaurṇamāsaṃ tatkLptenaivaitadyajñenāntataḥ pratitiṣṭhati tasmādudavasyati

Thereupon he shaves his hair and beard, and takes up the fire (of the uttaravedi),--for only after changing his place (to the ordinary sacrificial ground) he performs the (Full-moon) sacrifice on that fire, since it is not proper that he should perform the Agnihotra on the uttaravedi: for this reason he changes his place. Having gone to the house, and 'churned out' the fires, he performs the Full-moon offering. The Seasonal offerings, doubtless, are detached sacrifices; whereas the Full-moon offering is a regular, established sacrifice: hence he finally establishes himself by means of that regular sacrifice, and therefore changes his place (to the ordinary sacrificial ground).