Śatapatha Brāhmaṇa ("of a hundred paths") 7.5.2.38

7.5.2.38

pratyetyāgnimupatiṣṭhate | etadvā etadayathāyathaṃ karoti yadagnau sāmicite bahirvedyeti tasmā evaitannihnute 'hiṃsāyā āgneyyāgnaya evaitannihnute gāyatryā gāyatryo 'gniryāvānagniryāvatyasya mātrā tāvataivāsmā etannihnute 'niruktayā sarvaṃ vā aniruktaṃ sarveṇaivāsmā etannihnute yaviṣṭavatyaitaddhāsya priyaṃ dhāma yadyaviṣṭha iti yadvai jāta idaṃ sarvamayuvata tasmādyaviṣṭhaḥ

He returns (to the offering-fire) and stands thereby worshipping it;--for when he goes outside the Vedi, whilst Agni (the fire-altar) is only half built up, he does what is improper; he now makes amends to him to prevent his doing injury. With a verse to Agni (he worships): it is to Agni he thereby makes amends;--with an undefined one; the undefined means everything: by means of everything he thus makes amends to him;--with (a verse) containing the word 'youngest:' this indeed, to wit, the youngest, is his favourite form.;--inasmuch as when born he took possession (yu) of everything here, he is the youngest (yavishtha).