Śatapatha Brāhmaṇa ("of a hundred paths") 2.5.2.8

2.5.2.8

athaindrāgno dvādaśakapālaḥ puroḍāśo bhavati | prāṇodānau vā indrāgnī tadyathā puṇyaṃ cakruṣe puṇyaṃ kuryādevaṃ tattayorhaivāsya hetoḥ prajā na parābabhūvustatprāṇodānābhyāmevaitatprajā bhiṣajyati prāṇodānau prajāsu dadhāti tasmādaindrāgnau dvādaśakapālaḥ puroḍāśo bhavati

Then follows a cake on twelve potsherds for Indra and Agni. Indra and Agni indeed are the out-breathing and in-breathing: thus this is like doing a good turn to one who has done him a good turn; for it is owing to these two that his creatures did not perish. Hence he now restores his creatures by means of the out-breathing and in-breathing, bestows out-breathing and in-breathing on them: this is why there is a cake on twelve potsherds for Indra and Agni.