1,059. One Who Did Not Make an Eiruv Tavshilin

Shvisas Yom Tov 6:9

If a person did not make an eiruv tavshilin and others did not include him in an eiruv, then just as he may not cook or bake, his flour and food may not be used. One who made an eiruv is not permitted to cook or bake for a person without an eiruv (using that person’s ingredients) unless the one who did not make an eiruv transfers ownership of the food to the one who did make an eiruv. Once he does so, the one who made an eiruv will be cooking and baking using ingredients that belong to him. If he so desires, he may then give the food as a gift to the one who did not make an eiruv.

Shvisas Yom Tov 6:10

If a person did not make an eiruv tavshilin and he cooked and baked on yom tov for that day but there is food left over, or if he invited guests who did not come, he may eat the leftovers on the next day. If he intentionally over-prepared, he is not permitted to use this food. If the person violated the law and cooked or baked on yom tov for Shabbos without making an eiruv tavshilin, the food is not prohibited. The Sages were more stringent with one who tried to outsmart the law than with one who simply violated it outright because if leniency were granted those who acted disingenuously, everyone would do so and the entire idea of making an eiruv tavshilin would disappear. Not so many people are inclined to violate the law intentionally and the fact one chooses to violate it once does not necessarily mean that he will continue to do so.