This Upanishad belongs to the Atharva Veda. As the name of the Upanishad suggests, the teachings revealed in it are such as to leave its students clean, like a shaven head (mundaka), rid of the veil of ignorance. The lucid translation of the text along with Shankaracharya's commentary on it is an additional aid to comprehend the profundity of the subject.
The important thing is how much less you think of the body, of yourself as matter -- as dead, dull, insentient matter; how much more you think of yourself as shining immortal being. The more you think of yourself as spirit, the more eager you will be to be absolutely free from matter, body and senses. This is the intense desire to be free.
-Swami Vivekananda