By Rabbi Berach Steinfeld
The Midrash brings down in the name of Rav Yochanan that the malachim come before Hashem and ask, “When is Rosh Hashana and Yom Kippur?” Hashem responds to them that we need to ask the Bnei Yisroel, for the Bais Din establishes when Rosh Hashana falls out.
Why would the malachim ask about Yom Kippur, the Matteh Efraim asks. Shouldn’t Yom Kippur automatically fall out ten days after Rosh Hashana is established?
The Tzemach Tzeddek asks another interesting question. The Rashba and Rambam both hold that there is a chiyuv to eat a kzayis on Shabbos just like there is a chiyuv to eat a kzayis on the first night of Sukkos and Pesach. According to Shitas Reish Lakish that is permissible to eat a chatzi shiur on Yom Kippur min HaTorah, shouldn’t one eat a kzayis on Yom Kippur when it falls out on Shabbos since the prohibition min HaTorah of eating on Yom Kippur applies only to the size of a “koseves” (date), which is larger than a kzayis?
The answer to the first question could be based on the Rambam’s Shita that we can be mekadesh a month “lemafrea” (after it already happened.) The Rambam in Hilchos Kiddush Hachodesh, halacha tes vov until yud ches diagrams a scenario where Bais Din waited on the thirtieth day of the month and witnesses did not arrive. They then pronounced the month a “meuberes” (having an extra day: thirty days, not twenty nine.) If witnesses would arrive after a few days and testify that they came from a far away place and saw the moon on the night of the thirtieth, Bais Din, after ascertaining that they are saying the truth, will reschedule Rosh Chodesh a day earlier retroactively. There is a machlokes whether this would apply to all months or just for Nissan and Tishrei.
We see that the possibility exists for Rosh Hashana to be a day late if the witnesses did not arrive in time, and then Yom Kippur will fall out nine days after Rosh Hashana; hence the reason for the malachim asking Hashem when both Rosh Hashana and Yom Kippur will fall out.
The second question may be explained by analyzing the issur of carrying food on Shabbos. The Rishonim bring down that the shiur of food that is prohibited to be carried on Shabbos is the size of a “grogeres” (a fig). Nevertheless, if a Kohen carries teruma, he would be chayev even if it were a kzayis. The reason for this is because there is a mitzvah for the Kohen to eat the teruma, which in turn makes it chashuve enough to cause an infraction if one carries a kzayis on Shabbos.
Although we have learned that Resh Lakish says that eating less than a koseves is not assur min HaTorah; nevertheless, if we eat a kzayis for the Shabbos meal, then the kzayis becomes a shiur chashuv. It then will become sufficient enough for one to be oveir the issur of eating on Yom Kippur, the same way one is oveir for carrying less than the shiur because the kohen has a mitzvah of achilah of teruma.
May we all be zocheh for a full shiur of kaparrah on this Yom Kippur.