Hi Rabbi,
Is there an issue using a microwave on Yom Tov to heat up or cook food for that day?
I’ve read your answers on electricity and that the electricity itself isn’t the question, it’s whether an actual melacha is happening. On Yom Tov cooking for the day is allowed anyway, so it seems like a microwave should be simpler than a stove, not harder. But I wanted to ask before assuming, since the microwave also turns on a light, a fan and the display when you press start.
And is reheating in a microwave on Shabbat a different conversation, or does the same logic apply?
Thank you
Thank you Rabbi! The point that the microwave time is preset, so it shuts itself off before yad soledet bo, is exactly what I was missing. And learning what my own machine does during the week is advice I can actually use.
The short answer is: I see no problem using a microwave on Yom Tov to cook or heat food needed for that day.
Our actual position is that electricity itself is not fire and is not independently a melacha. My father, Rabbi Yitzhak Abadi zt”l, would sometimes make the rhetorical point that even according to those who want to treat electricity like fire, they still have to explain why electrically generated heat should be prohibited on Yom Tov when cooking for ochel nefesh is permitted.
The separate rule against creating a new fire on Yom Tov belongs to the broader framework of machshirei ochel nefesh, things that should have been prepared beforehand when possible. In earlier times, preparing a fire involved real work and could be done before Yom Tov. A microwave cannot meaningfully be “turned on beforehand” for food you intend to cook later. You activate it when you need it. So even through that framework, I do not see a reason to prohibit it.
The microwave’s light, fan, display and similar electrical functions do not change that conclusion. The real question is what the appliance is doing, and on Yom Tov cooking food for that day is permitted.
Shabbat is different, because cooking itself is prohibited.
If the food is already fully cooked and you simply want to warm it, I would permit using the microwave provided you know from ordinary weekday experience that the preset time will keep the food below approximately 125°F, which I use as the minimum practical shiur for yad soledet bo.
The important point is that the microwave heating time is preset. If you know that twenty or thirty seconds will only warm the food and will not bring it to yad soledet bo, the machine shuts itself off before reaching the temperature of bishul. That is different from putting something into a 350-degree oven and merely planning to remove it before it gets too hot.
I would not distinguish here between a fully cooked solid and a fully cooked liquid when the purpose is only warming and it remains below yad soledet bo. The Rema brings Rabbeinu Yerucham’s opinion that the concern with reheating liquids applies specifically where further cooking is:
מצטמק ויפה לו
where continued cooking or reduction actually improves the food (OC 318:4).
That is very different from taking yesterday’s fully cooked chicken soup and warming one bowl briefly. You are not continuing the cooking process or developing the food further. You are simply warming it.
In any event, since the case I am permitting stays below yad soledet bo, we do not need to resolve the entire liquid-versus-solid dispute.
Practically, every microwave is different. Learn yours during the week and know what twenty seconds, thirty seconds, and so on does to the foods you normally heat.
So: On Yom Tov, using a microwave to cook or heat food needed for that day is permitted. On Shabbat, with fully cooked food, I would permit brief microwave reheating when the preset time is known to keep the food below 125°F.
Shalom Rabbi,
On Shabbat, when dealing with fully cooked SOLID food you can go above 125°F?
My understanding is that the issue is with liquids (which the Rambam doesn’t see as a problem), but solid food is not an issue because it won’t really improve the food. I even read a Teshuvah of Rabbi Ovadia Yosef saying that you can toast your challah on the plata and I heard of Sephardic poskim that would allow to make grilled cheese sandwiches.
What is your opinion on this? Can you make such a sandwich or a pita pizza for the kids if the sauce is already cooked and doesn’t boil?
Yes, with a fully cooked dry solid food, the fact that it will become hotter than yad soledet bo is not itself a bishul problem.
Shulchan Aruch, Orach Chaim 318:15, says that something fully cooked and dry may be placed near the fire אפילו במקום שהיד סולדת בו, even in a place where it will become yad soledet bo. The reason is אין בישול אחר בישול בדבר יבש: once a dry food is fully cooked, reheating it does not constitute a new act of bishul.
But there is a separate question of where you put it.
Even if there is no bishul, I would not put refrigerated food directly onto a very hot plata or directly onto another surface normally used for cooking. That still looks like putting food onto the fire to cook or heat it. The Shulchan Aruch’s example is placing the food near the fire, not directly on the fire itself.
The simple solution is to create a separation. If you already have a pot of cholent or another pot sitting on the blech or plata, you can put the fully cooked dry food on top of that pot. You could also put down another pot or a foil pan and place the food on top of it. Then you are clearly not placing the food directly onto the cooking surface.
For example, fully cooked potato kugel from the refrigerator, wrapped in foil, can be placed on top of the cholent pot and allowed to become very hot. It does not matter if it eventually reaches yad soledet bo. It is already מבושל כל צרכו, fully cooked, and reheating a dry fully cooked food is not bishul.
So regarding grilled cheese or a pita pizza, I would not simply say, “It is fully cooked, therefore put it straight onto a hot plata.” The ingredients have to be analyzed, especially if there is sauce or another liquid component, and the food should not be placed directly onto a cooking surface in a manner that looks like ordinary cooking.
The basic rule is:
A fully cooked dry food may be reheated even above yad soledet bo.
But don’t put it directly onto the fire or a very hot cooking surface. Put it on top of another pot or create another clear separation.
That is the distinction I remember learning from my father, and it keeps the two issues straight: אין בישול אחר בישול is one question; placing food directly on a cooking surface is another.
Thank you for the answer Rabbi.
I guess that turning on the plata on Shabbat manually to reheat the food is not an issue. The issue would be how you place the food in the plata (not resembling cooking). Correct?
Exactly