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 — Яджнявалкья-упанишада47 versesJanaka asks Yājñavalkya about renunciation, and he answers: what is left behind, what is taken, how one lives. Here too is the famous passage that the true renounced one's thread is knowledge, not a cord.