Jewish Modes of Dress - Jewish Law As A Journey

And on the day of the LORD’s sacrifice I will punish the officials And the king’s sons, And all who don a foreign garment.

Idolatrous garbs

... The people of Israel would know they are guests and strangers in a strange land; they are like shoots of the olive tree that cannot be grafted unto any other tree.

One [i.e., a Jew] should not follow the customs of non-Jews (nor should one try to resemble them). One should not wear clothing that is particular to them [i.e., their culture]; one should not grow forelocks on one’s head like the forelocks on their heads; one should not shave the sides [of one’s head] and grow one’s hair in the middle of one’s head [like they do]; one should not shave the hair in front of one’s face from ear to ear and let one’s hair grow [in the back] [like they do]; one should not build places [i.e., buildings]—like the non-Jews’ temples—so that large groups of people will enter them, like [non-Jews] do. RAMA: Rather, one [i.e., a Jew] should be distinct from them [i.e., non-Jews] in one’s manner of dress and in all of one’s actions. But all of this [i.e., these restrictions] apply only to things that non-Jews do for the sake of licentiousness. For example, they are accustomed to wearing red clothing, which is official/princely clothing, and other clothing that is similarly immodest. [These restrictions also apply] to things that they are accustomed to doing because of a custom or rule that does not have a[ny underlying] reason, out of concern that [a Jew who does such things will follow the] “ways of the Amorites,” and that it has the blemish of [i.e., is tainted by] idol worship inherited from their ancestors. But things that they are accustomed to doing for a useful purpose—such as their custom for expert doctors to wear particular clothing so that the doctors will be recognized as specialists—one is permitted to wear [such clothing]. Similarly, things that are done out of respect or another reason, it is permitted [for one to do such things]. And therefore they said one may burn [the items of deceased] kings, and there is not in this “the ways of the Amorites.”

(4) "and lest you inquire after their gods, saying, etc.": that you not say: Since they go out in a toga, I will go out in a toga, too; since they go out in purple, I will go out in purple too; since they go out in fancy headdress, so will I.