Eruv Tavshilin, Demystified: When You Need It, How to Do It, and the Blessing

When a Yom Tov falls right up against Shabbat, the Sages prohibited preparing or cooking on Yom Tov for Shabbat, because it could look like you are downplaying the holiness of the day. So they instituted an Eruv Tavshilin: by setting it aside, you show that you already began your Shabbat prep before the holiday, and anything you cook on Yom Tov is just finishing what you started for Shabbat. With that act, cooking from Yom Tov for Shabbat is permitted. Therefore, when a holiday falls on Thursday and Friday and you want to cook for Shabbat, set aside an Eruv Tavshilin as explained below. (חזו\"ע יו\"ט רעד)

Who Is Exempt from an Eruv Tavshilin

Since the main purpose of setting an Eruv Tavshilin is so we may bake and cook from Yom Tov to Shabbat, if you already cooked all your Shabbat dishes before Yom Tov and have nothing left to cook for Shabbat, you do not need to set an Eruv Tavshilin just for lighting the Shabbat candles. If you still want to set one, do so without a blessing—when in doubt about blessings, we are lenient. (רעז) Still, if you want to gain the mitzvah, leave yourself one dish to cook from Yom Tov to Shabbat, for example, put raw eggs on Yom Tov into the cholent for Shabbat. Since you are still cooking something for Shabbat, you are obligated in Eruv Tavshilin with a blessing.

Guesthouse - A family staying at a guesthouse, with no need to cook at all for Shabbat, is exempt from setting an Eruv Tavshilin. (רעז)

Being a Guest - Guests staying with friends do not need to set their own Eruv Tavshilin; they can rely on the host’s Eruv Tavshilin and may help with the cooking, baking, and other preparations—just like members of the household. (רעז)

How Do You Make an Eruv Tavshilin?

On the eve of the holiday, take a cooked, roasted, or pickled food that is commonly eaten with bread, and also add a baked item in the amount of "kezayit" [27 grams]. Some have the custom to use a hard-boiled egg with bread. Today, since refrigerators keep food well, it is best to use a significant dish—like meat or fish—in honor of the mitzvah. (רעו, רפא)

The blessing - When setting the eruv, recite: "ברוך אתה ה' אלוהינו מלך העולם אשר קדשנו במצוותיו וציונו, על מצות עירוב". Then say the formula the Sages established in Aramaic; if you do not understand Aramaic, say the formula in Hebrew, as follows:

Eruv text in Aramaic: "בדין עירובא, יהא שרי לנא לאפויי, ולבשולי, ולאדלוקי שרגא, ולמעבד כל צרכנא מיום טוב לשבת".

Eruv text in Hebrew: "בזה העירוב, יהיה מותר לנו לאפות, ולבשל, ולהדליק את הנר, ולעשות כל צרכינו מיום טוב לשבת". (רפד)

It is good for the homemaker to hear the blessing and the eruv text from her husband, because the eruv is mainly done for her as she handles the household and cooking. Nevertheless, if she did not hear it, that does not invalidate anything, and she may cook and bake as usual. (רפו)

Timing Your Shabbat Prep

The eruv permits cooking for Shabbat only starting on the holiday itself—not earlier. Try not to leave the cooking to the late hours of Friday; make sure the food can fully cook on Friday, so that if guests were to arrive on Friday, they could eat that food. In any case, if you were delayed, you may prepare for Shabbat all day Friday, as long as the eruv still exists and has not been eaten. (רעח, רפא)

Other Preparations

It is permitted to roll the Torah scroll after the reading on Yom Tov [Friday] for the Shabbat reading, since—having set an Eruv Tavshilin—this is included in what is said in the eruv text, "ולעשות כל צרכנא". For the same reason, you may also wash the dishes and set the table on Yom Tov for Shabbat with the Shabbat tableware, arranging it as on any Friday, and similarly for comparable tasks. (שב)

Eating the Eruv

Try to eat the bread and the cooked item of the eruv at the Shabbat meal, because once one mitzvah was done with it, it is fitting to do another mitzvah with it. (רפב)

Forgot to Set an Eruv

Ideally, everyone should set an Eruv Tavshilin. However, if you forgot, you may cook and bake from Yom Tov to Shabbat, because in most communities the city rabbi grants his eruv to all residents, and they thereby fulfill their obligation. Even if you forgot several times over several holidays, you may rely, after the fact, on the city rabbi, since nowadays the rabbi intends to include even those who forgot. (רצא)

Intentional neglect - If one willfully failed to set an Eruv Tavshilin, the Sages penalized him, and he may not cook from Yom Tov to Shabbat. Nevertheless, he may cook for Yom Tov a large amount in one pot, even if his intention is to leave some for Shabbat. (רצד)

Eruv lost If the eruv was lost before he cooked for Shabbat, he should rely on the city rabbi’s eruv and cook. (רצב)

Helping Others Participate

If you want to enable someone who does not know how to make an Eruv Tavshilin, ideally, prompt him word by word for the blessing and have him repeat after you. Then the knowledgeable person says the eruv text like this: "בזה העירוב יהיה מותר לפלוני לאפות ולבשל ולהדליק את הנר, ולעשות כל צרכיו מיום טוב לשבת". If that person does not know how to bless at all, the knowledgeable person may also bless on his behalf. The Gaon the החיד\"א זיע\"א wrote that this was the custom in Jerusalem, the Holy City: to go from house to house and enable those who are not well-versed to make an Eruv Tavshilin. Blessed is the One who restores the crown to its former glory. (רצט)

Shabbat Timer

It is permitted to set a non-digital Shabbat timer on Yom Tov for Shabbat, for the hours it will turn on and off. (נז)

Although on Shabbat itself you should not change the timer’s state—except to extend the current state, that is, to lengthen its being off or on, but not to make it turn on earlier—aside from certain cases for an ill person or a mitzvah. Nevertheless, on Yom Tov, where the prohibition of ignition is rabbinic, it is permitted even to make it turn on earlier.