In the past, when the distance between communities was great, Ashkenazim lived in Ashkenaz, Sephardim in Spain, and Yemenites in Yemen. Any person who moved to another place would adopt the minhag of his new place and practice the customs of the local Jews regarding halachah and prayer. For example, people with the family name “Ashkenazi” follow the Sephardic customs yet are called “Ashkenazi” because they migrated from Ashkenaz to Spain. Likewise, families that migrated from Spain to Ashkenaz accepted upon themselves the Ashkenazic customs. Even if, over the course of time, many people migrate to a community and become the majority there, as long as they arrive as individuals, they are outweighed by the community in which they settle, and must practice according to the custom of the new place (Shulchan Aruch Yoreh De’ah 214:2; Orach Chaim 468:4; Mishnah Berurah 14).
The law is similar regarding a woman who married a man from a different ethnic group. She is considered someone who migrated from her community to his. She must abide by his practices, whether they are more strict or lenient, and she need not perform a hatarat nedarim (an annulment of vows) (Igrot Moshe, Orach Chaim, part 1, 158).[2]
When an entire community migrates to another place, since it is its own entity, it does not need to conform to the customs of the people there (Bei’ur Halachah 468:4). Even if the original people are the majority, as long as the new ones are united as an independent community, they should continue their initial minhagim. Similarly, that is the law in Israel today. By Hashem’s grace we merited a great ingathering of Jews from the Diaspora (kibbutz galuyot). Myriads of differing ethnic groups arrived, including talmidei chachamim, and each and every ethnic group founded its own synagogue. Therefore, no ethnic group is invalidated in regard to another and each must preserve its own minhagim.
[2]. However, if her husband does not mind, she may continue to pray according to her previous nusach (Halichot Shlomo 1, note 7). Nevertheless, it is proper for her to switch to her husband’s nusach before her children reach the age of understanding, so they will not be confused why their parents are praying in different nusachim (Tefillah Kehilchatah 4, note 4).However, if her husband does not mind, she may continue to pray according to her previous nusach (Halichot Shlomo 1, note 7). Nevertheless, it is proper for her to switch to her husband’s nusach before her children reach the age of understanding, so they will not be confused why their parents are praying in different nusachim (Tefillah Kehilchatah 4, note 4).
