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 Atman alone is eternal. Hospitals will tumble down. Railroad givers will all die. This earth will be blown to pieces, suns wiped out. The Atman endures for ever.
-Swami Vivekananda