I am invited to join friends for dinner, Monday evening the second night of Sukkot.
They will most likely prepare food on Monday during the the day. May I accept the invitation?
Answer:
It is fine to join your friends.
One reason for this is that you don’t know when they will be doing the cooking, and although you consider it likely, there is no certainty that they will cook from Monday to Monday night. Even if they do, it might be in a way that is permitted (for instance, if part of the food is being used for Yom Tov Rishon).
Another reason is that bedieved the food is permitted for consumption (the Rashba writes that this is a matter of doubt, and because the prohibition is rabbinic, the halachah is to be lenient; this is quoted by the Beis Yosef).
Best wishes.
