When a Jewish holiday falls out on a Friday (whether it’s the first or second day of Yom Tov) an Eruv Tavshilin is necessary in order to be able to cook or heat up food for Shabbos.
This year, 5785/2024, Jews all over the world will be making an Eruv Tavshilin on Erev Rosh Hashanah, and Jews in the Diaspora will also be doing so on Erev Sukkos and Erev Shemini Atzeres.
According to the Torah, it is permissible to cook on Yom Tov for Shabbos, but our sages were concerned that allowing this would lead people to mistakenly believe that they could cook for any day on Yom Tov. Therefore, they instituted Eruv Tavshilin, in which the cooking is begun before Yom Tov and continued on the holiday itself. There was also a concern that Shabbos preparations would be neglected in favor of holiday cooking, so the Eruv Tavshilin reminds us to honor Shabbos with special dishes as usual.
According to halacha, Eruv Tavshilin should be done even if you have no intention of cooking on Yom Tov for a few reasons:
It is a way to honor Shabbos
It gives you the option to cook/heat up food on Yom Tov for Shabbos, in case you need to
According to some poskim, lighting Shabbos candles is only permitted with an Eruv Tavshilin
Before Yom Tov, a cooked dish that can be eaten with bread must be prepared for the Eruv Tavshilin. The custom is to use a hard-boiled egg along with a piece of bread, but other cooked foods can be used too.
Pick up the food and say the bracha and the declaration that this food is an Eruv Tavshilin. The declaration is best said in Aramaic but can be said in Hebrew as well.
Click here to download a printable text of Eruv Tavshilin (PDF format).
Many people have the custom to eat the egg (or other cooked food) at one of the Shabbos meals and to use the bread for lechem mishneh at the third meal.
In every Jewish community, the rabbi makes an Eruv Tavshilin for the entire community, so if someone was unable to make one himself or forgot, he can rely on the rabbi’s Eruv Tavshilin to cook on Yom Tov for Shabbos.
Click here for a Crash Course in Hilchos Yom Tov.