Śatapatha Brāhmaṇa ("of a hundred paths") 6.6.3.17

6.6.3.17

prādeśamātryo bhavanti | prādeśamātro vai garbho viṣṇurannametadātmasammitenaivainametadannena prīṇāti yadu vā ātmasammitamannaṃ tadavati tanna hinasti yadbhūyo hinasti tadyatkanīyo na tadavati tiṣṭhannādadhāti tasyopari bandhuḥ svāhākāreṇa reto vā idaṃ siktamayamagnistasminyatkāṣṭhānyasvāhākṛtānyabhyādadhyāddhiṃsyāddhainaṃ tā yatsamidhastena nāhutayo yadu svāhākāreṇa tenānnamannaṃ hi svāhākārastatho hainaṃ na hinasti

They are a span long, for Vishnu, as an embryo, was a span long; and this is (Agni's or Vishnu's) food: he thus gratifies him with food proportionate to his own body. But the food which is proportionate to one's body satisfies, and does no injury; but what is too much that does injury, and what is too little that does not satisfy. Standing he puts them on--the significance of this (will be explained) further on;--and with the Svâhâ ('hail!'); for seed is infused here (in the sacrifice,--to wit,) this Agni; and were he to put on the logs unconsecrated by Svâhâ, he would injure him (Agni). Now inasmuch as they are kindling-sticks, they are not oblations; but inasmuch as (they are put on) with the Svâhâ, they are food, for the Svâhâ is food; and thus he does not injure him (Agni).