The Torah introduces us to the subject of the Bigdei Kehunah, the clothes to be worn by the Kohanim during the Avodah, with the commandment to Moshe "וע”ית בגדי קדש לאהרן אחיך לכבוד ולתפארת", "You shall make holy garments for your brother Aharon [which shall be] for honor and for beauty." (שמות כח' ב). At the end of the Perek (פסוק מ'), the phrase "לכבוד ולתפארת" is used once again, this time to emphasize that honor and beauty are in the uniform of the ordinary Kohanim as well. Certain later commentators (the Netziv, for example) are quick to point out that while the clothes may lend honor and glory to the person wearing them, the clothes do not "make the man." Aharon's Kedushah, his holiness and greatness, were enhanced by the clothes, but not caused by them. Others, such as the Malbim, emphasize the spiritual nature of "לכבוד ולתפארת"; the true honor and beauty are that of Hashem and His Torah.
Nevertheless, the Bigdei Kehunah were essential to the Avodah. No Kohein, not even Aharon, was allowed to perform the slightest part of the Avodah unless he was wearing these special clothes. In addition, the honor, dignity and beauty that these clothes imparted always had to be apparent. The Beis HaMikdash was the scene of constant activity, a working environment for the Kohanim that was frankly hostile to the concept of keeping one's clothes clean. Yet, unless the Kohein was wearing fresh, clean Bigdei Kehunah without a sign of wear or stain, the Avodah he performed was unacceptable. Moreover, as the Ramban indicates, the concept of "לכבוד ולתפארת" extends beyond the Kohanim to include the physical structure of the Mishkan and the Beis HaMikdash as well.
Without the Beis HaMikdash (מהרה יבנה!), the Avodah we perform is prayer, called עבודה שבלב, service of the heart. Without the Beis HaMikdash, there can be no Bigdei Kehunah. Their influence and effect, however, must still be present wherever prayer takes place. Every מקדש מעט, every Shul which has the Kedushah of a miniature Beis HaMikdash, from the smallest shtiebel to the largest Beis HaKnesses, must be לכבוד ולתפארת. The honor and beauty that is an absolute requirement for the Avodah must also be present in our עבודה שבלב, our Tefillah. This is manifested both spiritually, by our prayers and our Kavanah, that is, our exclusive attention to the Tefillah, and yes, physically as well, by what we wear and how we behave, and by the honor and beauty we create in the places in which we daven.