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1. The Gemara inquires about whether an Eruv Techumin is valid when a person makes his Eruv with a Tahor loaf of Terumah bread.
2. Rav Huna states that this Eruv (#1) is completely invalid.
3. Rav Nachman discusses cases in which a person says that his Eruv should be Hekdesh or Chulin today, but the opposite tomorrow.
4. Rav says that the validity of the Eruv depends on its status at the conclusion of Friday.
5. One may put two Eruvin in two opposite places and make a condition before Shabbos which determines which Eruv will take effect.
A BIT MORE
1. The case is where there are two loaves of Terumah in front of the person, one Tahor and one Tamei, and it is not known which one is Tamei. He proclaims that his Eruv should be with the Tahor loaf of Terumah, wherever it might be.
2. Since it is forbidden to eat the Tamei loaf, both loaves are considered inedible, since it is not known which one is the forbidden one. In order for the Eruv to be valid, the food must be permitted from before Shabbos.
3. If he says that it should be Chulin today (Friday) and Hekdesh tomorrow, the Eruv is valid. If he says the opposite, it is invalid.
4. It does not depend on the end of twilight, which may be considered the beginning of Shabbos.
5. If one is unsure about which direction marauders may come from, he may stipulate that if they come from the east, then his Eruv in the west will take effect, and if they come from the west, then his Eruv in the east will take effect.
Next Daf Index to Revach for Maseches Eruvin