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.
Eighteen verses — the shortest of the principal upaniṣads. The world in it belongs to the Lord, and a person in it is a guest: "all this is clothed by the Lord; enjoy what He has set aside for you." Hence its rule of life: work without appropriating, hold knowledge and deed together, without choosing between them.