938. An Opening That Closed and Reopened
Eiruvin 3:25
If the residents of two courtyards made a single eiruv together through an opening or a window between their domains, and then that opening or window became closed on Shabbos, the residents may continue carrying in their own courtyards. Since carrying was permitted for part of Shabbos, it continues to be permitted for the remainder of Shabbos. Similarly, if two courtyards each made their own eiruv and the wall between them collapsed on Shabbos, the residents of each may continue to carry within the area of their own original courtyards, i.e., between their homes and wherever they could carry before the wall collapsed since whatever carrying is permitted for part of Shabbos is permitted for all of Shabbos. Even though the number of people in the area has increased, this does not impede the ability to carry. If an opening between courtyards became closed on Shabbos and was later reopened unintentionally, or if another form of entry was made, or if non-Jews made an opening, it once again becomes permitted to carry between the two courtyards. Similarly, if two ships were tied together and an eiruv was made between them, it becomes prohibited to carry between them if their connection is broken on Shabbos, even if they are enclosed within a partition. If the connection is unintentionally reestablished, it once again becomes permitted to carry from ship to ship.
Eiruvin 4:1
If the residents of a courtyard eat at the same table, they do not have to make an eiruv as they are considered to be members of a single household. This is so even though they each have their own residence. Just as the presence of a one’s wife, the members of his household and his servants does not impede one’s ability to carry or make an eiruv necessary, the other residents of the courtyard are likewise considered members of a single household when they all eat at the same table.