In this week's parsha (weekly portion of the Pentateucha), the Torah puts much emphasis on the clothes the kohanim (priests) wore in the Mishkan (Tabernacle) & Mikdash (Holy Temple).
Why does it matter so much what the kohanim wore? Aren't we always told not to judge a book by its cover? And if the clothes are important, so why on Purim, the holiday in which we're supposed to reveal our inner selves, do we dress up in silly costumes?