In plain words
This Agni bears the office of charioteer for the yajñas and yāgas. The Ṛgveda holds that it is Agni who brings even the deities on his chariot. All the oblations that people offer in the yajña reach the deities through this Agni alone. What is the close bond here between the deities and the oblations Agni delivers? Because he himself, of his own accord, takes a kind of seat of authority over all these, and stands as the root and support of the yajñas, yāgas and other rites, the ṛtviks gave this very Agni the name Brahmā. Not only this: because he bears this authority, they have also called him Hotā. So these ṛtviks have invoked Agni in this yajña by many names.
This Agni has many kinds of bond with man. Without Agni, man cannot pass his life for even a single moment. From the moment day breaks, in the home it begins with fire. He cooks every food he eats, too. In the house, and in the kitchen too, Agni alone is foremost. It is the support. What is the inner meaning? They offer substances as oblations into Agni. One authority says that this Agni delivers them to the deities. Here, when we inquire into its chief supports in the life of man, our own digestive fire is the homa-pit in this. All the substances put into it, it reduces to ash, makes them take on the form of rasa, and has gone on supplying them to all the limbs.
By the authority of the Upaniṣad's word, 'rasō vai saḥ', God is the embodiment of rasa; this rasa, in every limb of man too, this rasa fills it and dwells there. That is why they gave him the name Aṅgīrasa. He is called Aṅgīrasa precisely because the Paramātma is present in every limb as the embodiment of rasa. Where did this form of rasa come from? From the digestive fire. Through this fire alone it has gone on supplying this form full of rasa to all these limbs.
In just the same way, the substances offered in the yāga he turns into rasa, and, through the smoke that is called this Agni, keeps spreading them to the whole world. Just because there are no leaders to teach such an inner meaning, the yajñas, yāgas and other rites have become a laughing matter. Not only that. Of the forbearance, sympathy and what is called equality that there were in the Vedic age of those days, not even a thousandth part is to be seen. The Veda taught the loftiest principle. It made known non-difference. It has made it known that oneness alone is its chief goal.
In the Śānti mantra: