Normally, it is forbidden to prepare food on Yom Tov for use the next day. However, when Yom Tov falls out on Friday, one may prepare for Shabbat on Yom Tov if he symbolically began the preparations before Yom Tov. This symbolic preparation is known as an eiruv tavshilin.

Every household must set aside one baked and one cooked item; usually an egg and a matzah/challah are used. The blessing of "al mitzvat eiruv" is recited and the items are held in the hand while saying the prescribed formula. One who forgot to prepare an eiruv tavshilin may still prepare for Shabbat if he lives in a city in which other Jews prepared them.

And now for more details:

1. Which activities does the eiruv permit?
All activities that are permitted on Yom Tov -- e.g. cooking, grinding and sorting, as well as washing dishes and lighting candles. Activities that are forbidden on Yom Tov do not become permitted due to the eiruv, such as turning on lights.

2. Who has to make an eiruv tavshilin?
Usually, every individual is obligated in this mitzvah. In practice, when the head of the household makes an eiruv, all the family members are included.

3. Who does not require an eiruv tavshilin?
A person who does not intend making any preparations on Friday for Shabbat, and does not need to kindle Shabbat lights. A person who needs only to kindle Shabbat lights, should make an eiruv without a blessing. This may be relevant for a person who is staying in a hotel or is invited out for all the Shabbat meals.

4. Is a visitor included in the host's eiruv?
No. Therefore, he must make his own eiruv if he intends to do some Shabbat preparations on Friday. Alternatively, he can become a partner in the family's eiruv by acquiring a share in the food.

DESIGNATING THE EIRUV

5. Which blessing is recited upon making the eiruv tavshilin?
While standing, and holding the food in the right hand, say:

Baruch ata Ado-noi Elo-heinu melech ha-olam, Asher kid-shanu bi-mitzvo-tav, Vi-tzee-vanu al mitzvat eiruv. Blessed are You, the Lord our God, King of the universe, Who sanctified us with His commandments, and commanded us in the mitzvah of eiruv.

6. Is anything else said?
Yes. Following the blessing, a declaration must be made describing the purpose of the eiruv foods. This declaration is traditionally said in Aramaic, but it must be said in a language that one understands. So if one does not understand the Aramaic words, he should say the following translation:

By means of these eiruv foods, we will be permitted to bake, cook, keep foods warm, light candles, carry, and do all that we need on Yom Tov for Shabbat.

7. Should the eiruv foods be held when reciting the blessing and eiruv declaration?
Yes. If you forgot to hold the foods, you should pick up the foods and repeat the declaration, but not the blessing.

8. What if a person did not say the eiruv declaration?
If it is not yet nightfall, he should take the foods in his hand and say it, but he should not repeat the blessing. If he remembers only after nightfall, he should preferably give his food to another person who should prepare it for him. If this is inconvenient, he may prepare as usual.

9. When should one make the eiruv?
On erev Yom Tov, preferably before the Yom Tov lights are kindled. If necessary, it may even be made on the night preceding erev Yom Tov. It is advisable for notices to be posted in shuls, to remind people to perform this mitzvah.

10. What if one made the eiruv before erev Yom Tov?
One should preferably make the eiruv again. The declaration should be repeated, but not the blessing.

11. May the eiruv be made on erev Yom Tov after sunset?
• It may be made until nightfall, if one forgot to do it earlier.

• However, if the congregation already began Ma'ariv with bar'chu, one should not make the eiruv, even if it is still before nightfall.

• In extenuating circumstances, the eiruv may still be made until nightfall,if the congregation has not yet reached the Amidah. • If one personally accepted Yom Tov (but the congregation did not), he may nevertheless make his eiruv until nightfall.

FOOD FOR THE EIRUV

12. Which foods should be used for the eiruv?
A cooked food and a baked food. The custom is to take meat, poultry, fish or egg for the cooked food, and a whole bread/matzah for the baked food. It is also permitted to use a roasted, pickled, fried or smoked food for the cooked food. Deserts may not be used.

13. Why are two types of food taken?
Taking a cooked food begins the cooking preparations for Shabbat, and taking a baked food begins the baking preparations.

14. What if a person did not take a cooked food?
The eiruv is invalid, and even baking for Shabbat is forbidden.

15. What if a person did not take a baked food?
•If he does not intend to bake for Yom Tov, the eiruv is valid. He may bake if he subsequently decides to do so.

•If he intends to bake, he should take a bread and repeat the appropriate part of the declaration, but the blessing should not be repeated. If this procedure was not done, he may nevertheless bake.

16. What is the most ideal type of cooked food to use?
In former times, the common practice was to use a hard-boiled egg, since this would certainly last for several days without spoiling. Today, when refrigerators are available, one should beautify the mitzvah by using a more superior type of food, like a portion of chicken or fish.

17. May one use a food that is frozen?
If one does not have any fresh food, one may use frozen food that is fully cooked.

18. What is the minimum size of the pieces of food?
The cooked food must be a kezayit (approx. 15 grams), and the baked food should preferably be a kebeitza (approx. 30 grams). These quantities are sufficient even if the eiruv is being made on behalf of many people.

19. Are any cooked foods invalid for the mitzvah?
One may not use a cooked food that is not usually served at a main course of a bread meal, e.g. oatmeal, cooked fruit.

20. When should the eiruv foods be prepared?
Although they may be prepared any time before Yom Tov, it is a greater mitzvah to prepare them on erev Yom Tov.

21. Must one cook the food personally?
No, one may use bought food. However, it is a greater mitzvah to personally prepare the food specifically for the eiruv.

SAVING THE FOOD

22. May one eat the eiruv foods on Yom Tov?
No. The foods must be kept in a safe place until Shabbat. Since the cooked food is usually kept in the fridge, it should be wrapped and labeled clearly, to prevent people from accidentally eating it.

23. What if some of the eiruv food was eaten?
One may prepare for Shabbat, provided that a kezayit of the cooked food remains.

24. What if the cooked food was entirely eaten or lost before Yom Tov began?
One should make the eiruv again, with a blessing.

25. What if the cooked food was entirely eaten or lost on Yom Tov?
•New preparations may not be made, but one may finish preparations that were begun when the eiruv food existed. Therefore, one may bake a dough/batter that was already prepared, and finish cooking a dish even if one only began peeling the vegetables.

• Food that was prepared during the time that the eiruv existed may be put aside for Shabbat, even if one originally intended to eat it on Yom Tov. Fresh food can then be made for Yom Tov.

26. What if the food spoiled before Shabbat?
It is as if the food was lost.

27. When may the food be eaten?
On Shabbat. The custom is to use the bread/matzah for lechem mishneh at each of the Shabbat meals and to eat it at seuda shlishit. The cooked food should preferably be eaten on Friday night.

NEGLECTING TO MAKE AN EIRUV

28. What if a person did not make an eiruv?
Usually, the local rabbi includes in his eiruv all the people in the town who did not make their own. However, a person who frequently or negligently forgets to make his own eiruv may not be able to rely on the eiruv that the rabbi makes. In any event, the rabbi must be consulted.

29. What if one remembers at Mincha on erev Yom Tov that he did not make an eiruv tavshilin?
One should stay in shul and daven Mincha with the congregation. In order to avoid the great inconvenience of not having an eiruv, it is permitted to recite an alternative eiruv declaration in shul. Upon returning home, he should put food aside for the eiruv.

30. What is the text of the eiruv statement in this case?
"The bread and cooked food that I will take when I come home will be my eiruv tavshilin from now."

31. May a person rely on the eiruv of the rabbi if he did not know that he had to make an eiruv?
Yes. Similarly, if he knew about the concept of eiruv tavshilin but assumed that the rabbi makes one for everyone, he is included in the eiruv of the rabbi.

32. What if a person lives in a place where there is no rabbi, or the rabbi did not include him?
It is forbidden for him to prepare for Shabbat in the usual way, since he does not have an eiruv tavshilin. The following options are available:

33. Are there any other options?
If Yom Tov is on Thursday and Friday, and he remembers on Thursday that he did not make an eiruv tavshilin, it is still possible to make one. (This is not the case on Rosh Hashana.) The details of this should be discussed with a rabbi.

34. May one light Shabbat candles if one did not make an eiruv?
No, since there is anyway electrical illumination. He may give his candles as a gift to another person, who may light them on his behalf. The precise details of this arrangement should be discussed with a rabbi.

35. When an eiruv is made, may the preparations be done close to Shabbat?
Every effort must be made to complete the preparations early enough on Friday afternoon that the food will be edible well before Shabbat. Similarly, water should be put on the stove so that it boils well before Shabbat. Nevertheless, if the preparations were left until late on Friday afternoon, they may still be done.

36. May one make Shabbat preparations on Thursday which is Yom Tov?
No, the eiruv only permits one to prepare on Friday. Even if a person knows that he will be unable to prepare on Friday and makes the eiruv with this in mind, he may not cook on Thursday for Shabbat. Preparations may begin on Thursday night.