It is forbidden on a holiday to do any act in preparation for the following day,1 even if the following day is Shabbat. However, the sages created a halachic device, called an eruv tavshilin, which allows one to cook food on a holiday day for use on a Shabbat that immediately follows it.
Reminder: Don’t Forget To Make An Eruv Tavshilin
It is forbidden on a holiday to do any act in preparation for the following day,1 even if the following day is Shabbat. However, the sages created a halachic device, called an eruv tavshilin, which allows one to cook food on a holiday day for use on a Shabbat that immediately follows it.
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