Leviticus 18:3 commands “Like the practice of the land of Egypt where you have dwelled, you should not practice, and like the practices of the land of Canaan to which I am bringing you, you should not practice, and in their laws you should not go.” This verse is both ambiguous (what practices?) and potentially far reaching (does it apply to practices of other non-Jewish nations as well?). A recent study by Beth Berkowitz examines the different ways Jews and Christians have understood this verse over the centuries. This discussion continues into modern times, as Jonathan Boyarin writes:
[Berkowitz’s] concluding—and longest—chapter deals with the complex, imaginative, and in certain ways surprisingly pragmatic and generous readings of the verse by perhaps the two most prominent decisors of the latter half of the twentieth century, Rabbi Ovadiah Yosef and Rabbi Moshe Feinstein. The former relied on his own assertion that non-European Jews had not been subjected to the same degree of pressure to assimilate as their Ashkenazi brethren in holding that some of the strictures based on observed non-Jewish practice need not apply to Sephardim in Israel. The latter permitted Orthodox Jewish men in America to dress in business suits just like those of their non-Jewish neighbors. Yet both evinced profound ambivalence about customs that, on one hand, had certainly not been observed by their ancestors (Thanksgiving is a prominent example), but on the other did not clearly involve halakhically prohibited acts and did not seem to be religious practices of non-Jews.
Read more on Marginalia: http://marginalia.lareviewofbooks.org/like-egyptians-jonathan-boyarin/