Rabbi Moshe Zywica 

1. What is the reason for Eruv Tavshilin?

1. When the second or eighth day of Yom Tov falls on Shabbos, or if Shabbos falls immediately after Yom Tov (as the third day of yom tov does this year on April 11th), it is rabbinically forbidden to cook or prepare on Yom Tov for Shabbos.  When executed properly, Eruv Tavshilin allows one to prepare on Yom Tov for Shabbos.

Interestingly, there is no Torah prohibition to cook or bake on Yom Tov for Shabbos, even though ostensibly one may only cook on Yom Tov for Yom Tov itself.  The Gemara (Pesachim 46b) offers two reasons why this does not constitute a Torah prohibition:

1. Shabbos and Yom Tov are considered to be one unit since Yom Tov is referred to as Shabbos in the Torah.  Just as it is permitted to cook and bake on Yom Tov for Yom Tov, it is permitted to cook and bake on Yom Tov for Shabbos.

1.  When one cooks or bakes additional food on Yom Tov, it is not a Torah violation because it is possible that one will need the food for unexpected guests who might arrive on Yom Tov.

 
If the Torah permits the preparation of food on Yom Tov for Shabbos, why did the Rabbis institute the Eruv Tavshilin in the first place?  The Gemara (Beitzah 15b) gives two explanations:

1. When Yom Tov precedes Shabbos, one is prone to overlook the needs of Shabbos.  The Rabbis therefore created a special tangible preparation for Shabbos that must be attended to before the start of the Yom Tov so people will remember Shabbos as well.

1. If we were to permit cooking on Yom Tov for Shabbos without any reminder, one might come to cook on Yom Tov for the subsequent weekdays, which would violate a Torah prohibition.

1. What is the procedure for Eruv Tavshilin?

1. On erev Yom Tov, Wednesday April 8th, one sets aside two types of food, one cooked and one baked (Mishnah Berurah 527:5-6).  If one cannot obtain both items, a cooked item alone would be acceptable, but a baked item alone would not suffice.  The cooked item must be at least the size of a large olive (approximately half the size of a chicken’s egg) and the baked item should be at least the size of a chicken’s egg.

The selected items are held in one’s hands while the bracha and subsequent Aramaic text, as they appear in the siddur, is recited.  It is necessary to understand the text as it is recited. If one does not understand the Aramaic text, it should be recited in one’s native language (Rama 527:12).

1. When is the Eruv Tavshilin effective?  Can I eat the Eruv Tavshilin food?
2. The Eruv Tavshilin allows one to prepare for Shabbos only on Erev Shabbos, but not on Thursday when it is the first day of Yom Tov (Shulchan Aruch 527:13).  In addition, every effort must be made to complete the preparations early enough on Friday afternoon so that the food will be edible well before Shabbos.  Nevertheless, if the preparations were left until late Friday afternoon, they may still be done (Beiur Halacha 527:1).

The food items used for the Eruv Tavshilin must remain intact as long as preparations are being made for Shabbos.  Perishable items used for the Eruv should be stored in the refrigerator as needed.  If the Eruv foods were consumed or discarded, the Eruv ceases to be valid (OC 527:15).
Matzah is used on Pesach as the baked item of the Eruv. It is customary to use this matzah for an additional mitzvah as one of the two ‘loaves’ of lechem mishnah at each of the three Shabbos meals, and to consume the matzah at the third meal of Shalosh Seudos.
 

1. If one is planning to be fully prepared for Shabbos before Yom Tov starts is an Eruv Tavshilin still necessary?
2. Rav Moshe Feinstein, zt”l understands the opinion of the Magen Avrohom (O.C. 527:1) to be that it is not absolutely necessary to make an Eruv Tavshilin if one is all prepared for Shabbos.  Nevertheless, Igros Moshe (Orach Chaim, 5:20:26) notes that even when a person is not planning to cook or bake on Yom Tov for Shabbos, an Eruv Tavshilin should be performed as a precaution for an unexpected need. Rav Moshe, z”tl in Orach Chaim, 5:37:9 writes that a bracha should not be recited in such a case.

1. What should be done if one forgot to perform an Eruv Tavshilin?
2. If one forgot to make an eruv before a Yom Tov (with exception of Rosh Hashana) that began on Thursday (as is the case with Pesach this year), it is possible to make an eruv on the first day of Yom Tov (Thursday). To do so, one should say the following: “If today (Thursday) is Yom Tov (and as such tomorrow {Friday} is a weekday), the eruv is unnecessary (because one may cook for Shabbos on a Friday which is a weekday). However, if today (Thursday) is a weekday and tomorrow is Yom Tov, this will be my eruv, which will allow preparation on Friday/Yom Tov for Shabbos. (Shulchan Oruch 527:22). Though others disagree, the Oruch Hashulchan (OC 527:36) recommends not making a bracha on this unique eruv because of the uncertainty if it is necessary. (The basis for making a conditional eruv is that halacha treats each of the first two days of Yom Tov as if they had an uncertain status). One then continues with the concluding text of the eruv. (There is no need to do anything additional on Friday because if Thursday was a weekday, he already made an eruv, and if Friday is a weekday, he does not need an eruv.)

An eruv cannot be made on the first day of Yom Tov which falls on Friday.
If one forgot to do the above process on Thursday, or if Yom Tov began on Friday, one may rely on the Eruv Tavshilin performed by the rabbi of the city, as it is customary for him to include his entire community in his eruv. One may rely on this only if the Eruv Tavshilin was not forgotten due to negligence (Shulchan Oruch ibid). In addition, one cannot rely on the rabbi’s eruv for two consecutive Yomim Tovim (MB 527:22). Kaf Hachaim 527:48 suggests that this limitation applies only if the two Yomim Tovim where consecutive. After forgetting to make an eruv two consecutive times, the Chayei Adam (Klal 102:7) questions whether one may rely again on the rabbi’s eruv in the future.
Another option is to have someone who made an Eruv Tavshilin cook for the one who forgot. In this case, ownership of the ingredients must be transferred to the one who is allowed to cook. This person may then proceed to cook even in the home of the person who did not make an Eruv Tavshilin (Shulchan Aruch OC 527:20).