Shabbat Reheating - Shabbat 37
First, the original text makes a distinction between a pot of water and a dish of food, since one is a matter of heating or cooling while the other may actively change through cooking. The Talmud then tries to claim that the Mishnah’s discussion applies to putting a pot or dish on the stove but not to simply keeping it there as Shabbat begins; later discussion makes clear that even a pot kept on the stove requires the active fire to be removed. Some clever person then imagined the case of TWO stoves joined to each other, where one is swept out but the other is not so that the heat of the stove with an active fire will still carry over to the other stove that has been properly treated – can one put something on the properly-treated stove? There is some debate as to the positions of Beit Hillel [the house/school of Hillel] and Beit Shammai according to Rabbi Judah and Rabbi Meir on this question – one says they would allow nothing or just water, where the other says one would allow water and the other water and a dish of food.
The larger question is: what constitutes forbidden cooking? What is the line between reheating and cooking in the days before microwaves and Tupperware leftovers? The Talmud’s rabbis observed details, and they noticed that cooked food has less bulk than raw food. So Rab and Samuel created a general rule that anything that, through heating, shrinks and is improved is forbidden to leave on a warm stove, and Rabbi Nahman adds that if it shrinks and deteriorates it is allowed. All of this makes us glad to live in communities where firing up the stove on Shabbat is a personal decision, with no communal condemnation awaiting.
Rabbi Adam Chalom