The Upaniṣads — the philosophical core of the Vedic tradition, revealing the nature of Brahman, the Ātman, knowledge, action and liberation. The ten principal Upaniṣads together with select minor Vaiṣṇava Upaniṣads.
1Chapter 1 — Пранагнихотра-упанишада40 versesOn "the libation into the fire of breath": an ordinary meal is described as a sacrifice, where the fire is digestion and the offering is the food itself. Hence the Vaiṣṇava practice of eating nothing that has not been offered.