Pesachim 51a, b

Hillel and his older brother Yehuda, sons of Rabban Gamliel, bathed together when in the town of Kabul.  Although this is permitted by Torah law, the custom in Kabul was to prohibit brothers from bathing together.  Hillel ran from the scandalized townspeople, afraid to tell them that their ruling was an error.  In the city of Birei, these brothers ran into a very similar problem when they wore wide shoes on Shabbat.

51(a) shows the rabbis' deliberations around keeping the halachot of a different town.  They consider whether Torah scholars also follow these erroneous decrees, whether or not the halacha is significant or insignificant, whether we are referring to Samaritans (Kuti) or Jews, whether some people (Chozai or Samaritans... or us?) would use extend a leniency.  Some of their suggestions include:

• visitors should follow significant customs that are guided by Torah scholars of that area
• visitors do not need to follow insignificant customs not guided by Torah scholars of that area
• when prohibition of a local stringency will result in a transgression, the stringency should be followed
• a man cannot bathe with his father, step-father, father-in-law, step-father, or sister's husband (though leniencies exist when pants are worn in the bathhouse)

The rabbis share examples of cultural differences and thoughts on managing different practices:

• sitting on Gentiles' stools in Akko
• Rabbi Yehuda ruling that one can bathe with one's father (and from the Tosefta; with one's teacher) to help assist him with bathing
• Rabba Bar Channa's eating of disputed fat
• Eretz Yisroel's customs are dominant to those of Babylonia when one travels
• in the presence (The Me'iri: during my lifetime) of Rabbi Shimon ben Yosei ben Lakonya, Rabbi Yochanan ben Elazar was permitted to eat the after-growth of cabbage in the Sabbatical year

How do we resolve these differences?  The Gemara tells us that if one intends to return home, one should keep his or her own customs -- but privately -- while in another town.  Abaye notes that we should be stringent regarding this last point based on Proverbs 1:8, "Listen my son to the rebuke of your father".  Clearly the rabbis are torn between maintaining one's own practices/respecting the wishes of one's parents and minimizing dispute with other Jewish communities.

Again, we are faced with similar circumstances today.  To what degree is minhag important?  And does one leniency beget a larger lenience, which begets another leniency... But while the rabbis believe that this is a negative development, I can't help but wonder whether Judaism at its core has survived because of people's creativity regarding practice in different places at different times.  Certainly something to reflect upon with some seriousness.