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1. It is forbidden for a person to nullify a forbidden item l'Chatchilah.
2. There is a dispute about an egg laid on the first day of Yom Tov outside of Eretz Yisrael.
3. Rav Asi is stringent (#2) despite the fact that he used to recite Havdalah between the two days of Yom Tov.
4. Two days of Yom Tov were originally observed outside of Eretz Yisrael, because they did not know when the Beis Din had declared Rosh Chodesh and when Yom Tov would fall.
5. We still keep two days of Yom Tov nowadays outside of Eretz Yisrael.
A BIT MORE
1. For example, one may not put a small amount of milk in a meat dish, even though the milk will become nullified in sixty parts of meat.
2. Rav: It is permitted on the second day. Rav Asi: It is forbidden.
3. Rav Asi would recite Havdalah between the two days because he considered them two separate days, with the first being the real day. However, he said that it is possible that the Chachamim wanted us to treat the second day stringently, as if the two days were one long day.
4. Since Yom Tov was based on the date of Rosh Chodesh the previous month, which was based on when the witnesses' testimony regarding the new moon was accepted by Beis Din, only people who knew what day had been declared as Rosh Chodesh could know for certain the correct day of Yom Tov. Accordingly, people outside of Eretz Yisrael who were not informed would have to keep two days of Yom Tov out of doubt.
5. This is because it is the custom of our forefathers, and we might end up needing two days if the governing body outlaws the calculation of the Jewish calendar.
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