Eiruvin 3:7-8

Eiruvin 3:7

[The following mishna refers to the time of the Sanhedrin, when the new month was announced based on witnesses testifying about seeing the moon.]

Rabbi Yehuda says that if a person was concerned that the month of Elul would be 30 days rather than 29, with the result that Rosh Hashana would be two days instead of one, he could make two different eiruvs, 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 did not agree with him, considering both days of Rosh Hashana to be a single state of sanctity, which cannot be split.

Eiruvin 3:8

Rabbi Yehuda continued that if one had a basket of untithed produce, he could tithe it conditionally on the first day of Rosh Hashana and eat it on the second. (Tithing conditionally involves saying “If today is a weekday, let this be tithes for this produce; if today is Rosh Hashana, let my words be meaningless.” He does this again on the next day, with the result that the produce was tithed on one day or the other, so it can certainly be eaten on the second day.) He also said that an egg laid on the first day could be eaten on the second. (An egg laid on yom tov may not be eaten the same day. In this case, the egg was either laid on a weekday or eaten on a weekday.) The Sages did not agree with Rabbi Yehuda, again considering both days of Rosh Hashana to be a single state of sanctity that cannot be divided. (The Sages only disagree in the case of Rosh Hashana; they agree with Rabbi Yehuda when it comes to the two days of other Festivals observed outside of Israel.)