What is an Eruv Tavshilin?
This year (5780), the first day of Shavuot will fall out on Friday, Erev Shabbat. We know that it is permissible to cook on Yom Tov. (It is nevertheless forbidden to create a new fire; rather, one may transfer a pre-existent flame lit before the onset of Yom Tov. It is likewise forbidden to extinguish a flame on Yom Tov, as we have discussed on several occasions.)
When Yom Tov falls out on a Friday as it does this year, many people wish to cook on Yom Tov for the upcoming Shabbat. However, our Sages prohibited cooking on Yom Tov for Shabbat without placing an “Eruv Tavshilin,” which is placing (designating) bread and a cooked food on Erev Yom Tov (Thursday) for Shabbat (i.e. to be eaten on Shabbat) in order for it to be recognizable that one is not beginning to cook or bake on Yom Tov for Shabbat; rather, one is merely concluding this preparation.
Explanation of the Above
In honor of Yom Tov, our Sages prohibited cooking on Yom Tov for Shabbat (in order for Yom Tov not to appear like a regular weekday with regards to Shabbat). However, if one begins cooking for Shabbat on Erev Yom Tov (i.e. before the onset of the holiday) and merely concludes on Yom Tov, this does not constitute a lack of respect for Yom Tov. We therefore leave bread and a cooked food on Erev Yom Tov to be eaten on Shabbat in order to show that one has already begun preparing foods for Shabbat before the onset of Yom Tov and that on Yom Tov itself, one is merely finishing off what one has already started. If one did not place an Eruv Tavshilin, one may not cook on Yom Tov for Shabbat.
The Proper Way to Prepare the Eruv
There are several laws regarding the bread and cooked food one must leave for the Eruv Tavshilin. It is customary to leave bread (amounting to a weight of approximately fifty-four grams) and a hard-boiled egg. When one takes the bread and hard-boiled egg on Erev Yom Tov (Wednesday), one recites: “Baruch Ata Hashem Elokeinu Melech Ha’Olam Asher Kideshanu Be’mitzvotav Ve’tzivanu Al Mitzvat Eruv.” One must include Hashem’s name while reciting this blessing. After reciting the blessing, one should say: “With this Eruv, we shall be permitted to bake, cook, light candles, and do anything necessary on Yom Tov for Shabbat.” One then saves the bread and cooked food and (preferably) eats them on Shabbat night or any other time on Shabbat.
A Public Eruv
In most places, the rabbis of the city customarily make an Eruv Tavshilin in a special way that will benefit those who have forgotten to make one. Thus, if one forgets to make an Eruv Tavshilin but the local rabbi has made an Eruv in this way, one may rely on the Eruv of the rabbi and one may cook on Yom Tov for Shabbat. Nevertheless, it is preferable for each individual to make an Eruv Tavshilin in his own home.
Concluding Shabbat Preparations as Early as Possible
Although one has made an Eruv Tavshilin, it is preferable to finish all works one is performing on Yom Tov for Shabbat as early on in the day as possible and not to carry on until close to the onset of Shabbat. Nevertheless, if one was delayed for whatever reason, one may continue to prepare until a several minutes before sunset.
Candle-Lighting for Shabbat this Year
The Shabbat candles should be lit approximately twenty minutes before sunset of Friday, the first day of Shavuot, for after this time, the day already takes on the sanctity of Shabbat and lighting candles is forbidden. One may prepare the Shabbat candles during Yom Tov itself.