Shatapatha Brahmana 6.5.3.7

6.5.3.7

prajāpatireṣo 'gniḥ | ubhayamvetatprajāpatirniruktaścāniruktaśca parimitaścāparimitaśca tadyā yajuṣkṛtāyai karoti yadevāsya niruktam parimitaṃ rūpaṃ tadasya tena saṃskarotyatha yā ayajuṣkṛtāyai yadevāsyāniruktamaparimitaṃ rūpaṃ tadasya tena saṃskaroti sa ha vā etaṃ sarvaṃ kṛtsnam prajāpatiṃ saṃskaroti ya evaṃ vidvānetadevaṃ karotyathopaśayāyai piṇḍam pariśinaṣṭi prāyaścittibhyaḥ

That Agni is Pragâpati; but Pragâpati is both of this, defined and undefined, limited and unlimited: thus when he makes (bricks) from (clay) prepared with prayer, he thereby makes up that form of his (Pragâpati's) which is defined and limited; and when he makes them from (clay) prepared without prayer, he thereby makes up that form of his which is undefined and unlimited. Verily, then, whosoever knowing this does it on this wise, makes up the whole and complete Agni. From the (clay) lying ready prepared, he leaves over a lump for expiations.