Eiruvin 3:5-6
Eiruvin 3:5
A person can place his eiruv with conditions, such as “If raiders come from the east, my eiruv is to the west; if they come from the west, my eiruv is to the east. If they come from both directions, my eiruv is in the direction that I choose to go. If they come from neither direction, I am like all the other residents of my city.” Another stipulation would be “If a scholar comes from the east, my eiruv is to the east; if he comes from the west, my eiruv is to the west. If a scholar comes from each direction, my eiruv is in the direction that I choose to go. If one comes from neither direction, I am like all the other residents of my city.” Rabbi Yehuda says that if two scholars come from opposite directions and one of them is his teacher, he goes to his teacher. If they are both his teachers, he may go in the direction he chooses.
Eiruvin 3:6
Rabbi Eliezer says that if yom tov is next to Shabbos, whether before or after it, a person may make two eiruvs in two different directions, such as: the first going east and the second going west; the first going west and the second going east; an eiruv for the first day and the second day like all the other residents of the city; an eiruv for the second day and the first day like all the other residents of the city. The Sages say that he can make an eiruv in one direction or not at all, for both days or not at all. A two-day eiruv is set as follows: he takes it to the designated place on the eve of the first day. He waits for yom tov to start, then he goes home, carrying the eiruv with him. On the eve of the second day he takes the food there, waits for Shabbos to start, and eats it there. His eiruv on the first day enables him to walk there on the second day. If the eiruv was eaten on the first day, it is not valid for the second day. Rabbi Eliezer pointed out to the Sages that, since they maintain that an eiruv that was eaten no longer works for the second day, it shows they agree with him that the two days can have different eiruv arrangements.