The Mundaka Upanisha मुण्डक-उपनिषद्, Muṇḍaka Upaniṣad is an ancient Sanskrit Vedic text, embedded inside Atharva Veda. A poetic verse style Upanishad, with 64 verses, written in the form of mantras.
The first Mundakam defines the science of "Higher Knowledge" and "Lower Knowledge", and then asserts that acts of oblations and pious gifts are foolish, and do nothing to reduce unhappiness in current life or next, rather it is knowledge that frees.
The second Mundakam describes the nature of the Brahman, the Self, the relation between the empirical world and the Brahman, and the path to know Brahman.
The third Mundakam expands the ideas in the second Mundakam and then asserts that the state of knowing Brahman is one of freedom, fearlessness, complete liberation, self-sufficiency and bliss