Śatapatha Brāhmaṇa ("of a hundred paths") 1.4.1.38

1.4.1.38

samidhyamāno adhvara iti | adhvaro vai yajñaḥ samidhyamāno yajña ityevaitadāhāgniḥ pāvaka īḍya iti pāvako hyeṣa īḍyo hyeṣa śociṣkeśastamīmaha iti śocantīva hyetasya keśāḥ samiddhasya samiddho agna āhutetyataḥ prācīnaṃ sarvamidhmamabhyādadhyādyadanyatsamidho 'pavṛṅkta iva hyetaddhotāyadvā anyatsamidha idhmasyātiricyate 'tiriktaṃ tadyadvai yajñasyātiriktaṃ dviṣantaṃ hāsya tadbhrātṛvyamabhyatiricyate tasmādataḥ prācīnaṃ sarvamidhmamabhyādadhyādyadanyatsamidhaḥ

[He recites the ninth kindling verse]: 'He who is kindled at the cult'--the cult (adhvara), doubtless, is the sacrifice: 'he who is kindled at the sacrifice' he thereby says;--'Agni, the bright, the laudable,' for he is both bright and laudable;--'the flaming-locked, him we adore!' for when he is kindled, his locks, as it were, flame. Previously to (the beginning of the tenth verse), 'O Agni, worshipped, thou art lit!' let him (the Adhvaryu) put on all the kindling-sticks with the exception of the one stick (which is to be put on at the after-offerings); for it is now that the Hotri completes (the kindling); and what then is left of the kindling-sticks, other than the one stick, that is left (unused altogether); and what is left (unused) of the sacrifice, that is left for his (the sacrificer's) spiteful enemy: let him, therefore, previously to this (verse), put on all the samidhs, save one.