Rebbe Nachman Of Breslov On Clothing
A Yid commenting on Imposing A Dress Code:
When questioned on this subject, Reb Elozer Kenig answered that a Chassidisher levush is a holy and important component of the Rebbe's derech. Some people from a more modern background who are attracted to Breslov may hesitate to change their style of dress. This hesitation should not be an obstacle. One need not wear a long black jacket to study the Rebbe’s teachings and follow his guidance in ‘avodas HaShem. However, even if one is not ready to make such external changes at present, one may aspire to wear a Chassidisher levush. In any case, one should respect the traditional Jewish manner of dress.
Here are some quotes from the Breslover minhogim project on this subject (reference to Chayey Moharan isn't done properly according to sections, and uses "through" numbering):
The Rebbe cautioned his followers not to wear unclean, torn, or shabby clothes. Rather, a G-d-fearing person should wear clean and respectable clothing, according to his ability.
(Chayei Moharan 201)
The Rebbe praised the Chassidim for preserving the traditional Jewish style of dress and appearance, and for keeping distant from chokhmos chitzoniyos.
(Chayei Moharan 421)
Reb Noson discusses the mystical meaning of the centuries-old Jewish custom to fasten one’s shirts and jackets so that the right side is on top of the left side. This indicates the dominance of midas ha-chesed over midas ha-din. Chassidim are particular to use such garments, as opposed to those worn in the secular world, which fasten left over right.
(See Likkutei Halakhos, Hilchos Hashkomas ha-Boker 1:10)
The Rebbe once remarked that there is a connection between the fact that Jews in Germany in his day already wore short jackets in the modern, western European manner, and that the Zohar was not commonly available there.
(Chayei Moharan 422)
The Rebbe delivered awesome mystical teachings about the beard and peyos. He also related the removal of the beard to assimilation and religious decline.
(E.g. see Likkutei Moharan I, 20; Chayei Moharan 51, 86; et al.)
Reb Noson expounds at length upon the mystical meaning of the beard and peyos, which he relates to the Patriarchs Avraham, Yitzchak, and Yaakov, and the right, left, and middle columns in the array of the sefiros. He points out that these are not only symbols, but also channels for spiritual illumination.
(Likkutei Halakhos, Gilu’ach 1, 3, et passim)