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.
So long as the millions live in hunger and ignorance, I hold every person a traitor who, having been educated at their expense, pays not the least heed to them!
-Swami Vivekananda