Recently I’ve been asked questions about reheating food on Shabbat.
Below are some guidelines that all of us should bear in mind.
Any food that you want to reheat on Shabbat must have been completely cooked before
Shabbat. Even if it is mostly cooked that is not good enough. Completing the cooking
by returning it to any source of heat (over 105 degrees F. or what is known in Halacha as
yad soledet bo) on Shabbat is a violation of the Torah prohibition against cooking.
If the food is fully cooked, if it is a liquid or contains visible liquid such as gravy or
sauce, reheating such food is forbidden. Liquids that get cooked or boiled and then cool
down are subject to cooking again and again. Therefore, no food containing liquid should ever be returned to a heated area which is above 105 degrees on Shabbat
If the food is totally dry and has been fully cooked, then it is possible to reheat it but only if certain conditions are met.
It can, according to some lenient positions, be returned to the burners of a stove provided they are covered with a blech, and that food had already been placed on the blech Friday evening as Shabbat began (and was later taken off and put in the refrigerator with the intention of returning it to the blech on Shabbat day).
It cannot be returned to the inside oven of the stove even if your stove has a Shabbat mode on it. Since the oven is a normal place where cooking occurs and its appearance on Shabbat is no different than on weekdays, this is forbidden.
On the other hand, if the reheating device is not a regular stove or oven and the above condition of fully cooked dry food is met, there is no such concern for “the appearance of cooking.” Therefore, to place this kind of food on a heating plate (a ‘plata’ as it is called in Hebrew) or inside a warming drawer is permissible according to many Poskim, even if the temperature is well above 105 degrees. Any knobs or controls to such devices should be taped or covered to remind us not to manipulate them on Shabbat.
As simple as I try to make these rules, I realize that they may sound complicated and confusing to some of you.
Please feel free to call me regarding any questions or concerns you may have.