We read in the Torah section of Tetzave (Sh’mot 28:2-4), “And you shall make vestments of sanctity for Aaron your brother, for glory and splendor. And you shall speak to all the wise-hearted people whom I have invested with a spirit of wisdom, and they shall make the vestments of Aaron to sanctify him to minister to Me. These are the vestments that they shall make: a Breastplate, and Ephod, a Robe, a Tunic of a box-like knit, a Turban, and a Sash.” G-d commanded that special lavish garments were to be made for Aaron and his offspring to wear while performing their service in the Mishkan (Tabernacle) and later in the Bet HaMikdash (Temple), and, if these garments were not worn, the service would be rendered invalid. Whereas, the kohen gadol (high priest) was to usually wear eight such garments, except on Yom Kippur when he wore four special white garments, any other kohen (priest) was to wear four such ornate garments.
In explanation of this emphasis on grandeur with regards to the priestly garments, Maimonides notes in his Moreh Nevukhim (3:45), “In order to raise the estimation of the Temple, those who ministered therein received great honor; and the priests and levites were therefore distinguished from the rest….[Moreover,] a priest that had a blemish was not allowed to officiate; and not only those that had a blemish were excluded from the service, but also – according to the Talmudic interpretation of this precept – those that had an abnormal appearance; for the multitude does not estimate man by his true form but by the perfection of his bodily limbs and the beauty of his garments, and the Temple was to be held in great reverence by all.” While G-d did not need this grandeur nor was this necessary for the sake of the lofty individuals serving Him, we needed such grandeur in order to ensure and maintain the proper stature in the eyes of the populace at large for the Temple and its service to G-d and all that is connected with it.
Similarly, our Sages tell us (Babylonian Talmud, Shabbat 113a), “’And you honor it [the Sabbath] by not engaging in your own affairs’ [Yeshaya 58:13] … [this teaches us] that your garments of the Sabbath should not be like your garments of the weekday.” In order to ensure and maintain the esteem that the holy Sabbath should be held in on the part of the general populace, all are expected to dress in a more dignified manner on the Sabbath (see Shulchan Arukh, Orach Chayyim 262:2). We are thereby reminded by our actions to respect this holy day and those who see us doing so are given the message that this is an important day.
We also find that our Sages look down on a talmid chakham (Torah scholar) whose garment is stained (Babylonian Talmud, Shabbat 114a). Our Sages understand that a chilul HaShem (profanation of G-d’s name) can result, since a Torah scholar whose clothes are dirty or stained reduces the respect in others’ eyes for Torah scholars and, in turn, for the Torah – G-d’s Word – that they study. And, although a talmid chakham is technically one who is fluent in the entire Torah and can answer all questions that he is posed without hesitation (Babylonian Talmud, Shabbat 153a), leading some to believe that the Sages’ stringency regarding a scholar’s mode of dress is more limited, we find that the great latter day Torah giant R. Yisrael Meir Kagan, known as the Chafetz Chaim, thought differently. Once when he saw his son do something, the Chafetz Chaim told him, “A talmid chakham like you should not do that because it can cause a chilul HaShem.” When his son countered, “But Father, I am not a talmid chakham!” the Chafetz Chaim replied, “For chilul HaShem, you are enough of a talmid chakham.” To amplify upon this, the renown rosh yeshiva R. Avraham Pam notes (Sholom Smith, A Vort from Rav Pam, p. 113) that today every Jew who wears a yarmulke on his head and especially one with a beard must understand that he is under public scrutiny, and despite not considering himself learned or worthy of the title of talmid chakham, the world at large sees him as a symbol of Torah and a representative of G-d and His Torah, and acting in a manner perceived to be unbecoming may lead to a negative view of what he represents.