Śatapatha Brāhmaṇa ("of a hundred paths") 7.2.4.30

7.2.4.30

prajāpatireṣo 'gniḥ | ubhayamvetatprajāpatirniruktaścāniruktaśca parimitaścāparimitaśca tadyadyajuṣā karoti yadevāsya niruktam parimitaṃ rūpaṃ tadasya tena saṃskarotyaśca yattūṣṇīṃ yadevāsyāniruktamaparimitaṃ rūpaṃ tadasya tena saṃstaroti sa ha vā etaṃ sarvaṃ kṛtsnam prajāpatiṃ saṃskaroti ya evaṃ vidvānetadevaṃ karoti bāhyāni rūpāṇi niruktāni bhavantyantarāṇyaniruktāni puśureṣa yadagnistasmātpaśorbāhyāni rūpāṇi niruktāni bhavantyantarāṇyaniruktāni

This Agni is Pragâpati, and Pragâpati is both the defined and the undefined, the limited and the unlimited. Now whatever he does with prayer thereby he restores that form of his which is defined, limited; and whatever he does silently, thereby he restores that form of his which is undefined, unlimited,--verily, whosoever, knowing this, performs thus, restores this whole and complete Pragâpati. The outer forms are defined, and the inner ones are undefined; and Agni is the same as an animal: hence the outer forms of the animal are defined, and the inner ones undefined.