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.
A book of the beginning: from Nārāyaṇa come the elements, the worlds, and the person, and in Him all things end. Hence its refrain — "all is Nārāyaṇa"; the second half is on renunciation and on how one who has left everything lives.