Igrot Moshe Choshen Mishpat 1:72
אגרות משה חושן משפט א:עב
א[ין] צ[ורך] שיעשה המנהג ע[ל] פ[י] חכמי התורה וגם אף לא ע[ל] פ[י] יהודים דוקא, דאף שהנהיגו זה הנכרים – כגון שהם רוב תושבי העיר – נמי הוא מדין התורה בסתמא כפי המנהג, דאדעתא דמנהג העיר נחשב כהתנו בסתמא... ולכן אין חלוק מי הם שהנהיגו
It is not necessary that the custom be based on the sages, nor even based on Jews, for even if gentiles established the custom – as, for instance, where they are in the majority in that location – it is still Torah law that the standard should follow the custom, for absent another provision it is as if they conditioned [the contract] on the prevailing custom… therefore it does not matter who it is who has established the custom. [translation by Hekhsher Tzedek "Al Pi Din" by Rabbi Avram Israel Reisner for Heksher Tzedek Commission of RA/USCJ]

Suggested Discussion Questions:

1. What types of customs is Rav Moshe referring to?

2. In what ways do we follow Rav Moshe in our business practices today? In what ways do we fail to do so?

Time Period: Contemporary (The Yom Kippur War until the present-day)