הלכה על צפניה 1:8

He prohibited us from following in the ways of the idolaters, and from behaving according to their practices - and even with their clothing and with their gatherings in their assemblies. And that is His, may He be exalted, saying, "You shall not follow the practices of the nation(s)" (Leviticus 20:23). And in the explanation (Sifra, Acharei Mot, Section 8:8), it appears - "I only said those that were established for them from their forefathers." And the language of the [Sifra] (Sifra, Acharei Mot, Chapter 13:8) is, "'And in their statutes you shall not walk' (Leviticus 18:3) - in their customs, those things that are established for them, such as theatres and circuses." And these were types of assemblies in which they would gather for worship of the images. "Rabbi Meir says, 'These are the ways of the Amorites, which the Sages enumerated.' Rabbi Yehudah says, 'that you not round [your face], and not cultivate locks, and not wear the hair komi.'" And one who does one of these things is liable for lashes. And the prohibition of this content was repeated in another place. And that is His saying, "Take heed unto yourselves, lest you are drawn in after them" (Deuteronomy 12:30). Lest you resemble them and do their deeds and it becomes a stumbling block; that you should not say, "Since they are going out with telusin, I will also go out with telusin" - and that is a type of weapon of the Persians. And you already know the language of the prophet (Zephaniah 1:8), "and all such as are clothed in foreign garments." And this is all to distance ourselves from them and to revile all of their practices, and even their clothes. And the regulations of this commandment have been explained in the sixth [chapter] of Shabbat. (See Parashat Kedoshim; Mishneh Torah, Foreign Worship and Customs of the Nations 11.)

To not follow the practices of the gentiles: To not follow the practices of the Amorites and so [too,] the practices of the gentiles, as it is stated (Leviticus 20:23), "And you shall not follow the practice of the nation that I am driving out before you." And the law is the same for all the nations, since the matter is that they turn away from [following] God, and worship idolatry. And the content of the commandment is that we not behave like them in our clothing and our matters. And it is like they said in Sifra, Achrei Mot, Chapter 13:8, "'And do not follow their practices - that you not follow their mores with things that are fixed for them, such as theaters, circuses and amphitheaters" - and all of these are types of frivolity that they would do in their gatherings, when they gathered to do craziness, licentiousness and idolatry. And they said there, "'The practice of the nation' - Rabbi Meir says, 'These are the ways of the Amorites that the sages numbered (see Shabbat 67a).' Rabbi Yehudah ben Betira says, 'That you should not grow a tassel of the head and not cut its growth'" - meaning to say that he not shave from the sides and leave hair in the middle, which is called a forelock. And this negative commandment is repeated in another place with other words, as it is stated (Deuteronomy 12:30), "Guard yourself lest you be ensnared to follow them." And the language of Sifrei is "'Guard' is with a negative commandment; 'lest' is with a negative commandment; 'you be ensnared to follow them' is lest you imitate them and do like their deeds; 'and it shall be a snare for you' is that you not say, 'Since they go out with velvet, I will go out with velvet, since they go with helmets, I will go with a helmet'" - and that is a type of knight's armor. And the language of the books of prophecy (Zephaniah 1:8) is "and upon all of the dressed, there is a foreign dress."