by R. Daniel Mann
Question: May we use a frozen challa for lechem mishneh on Shabbat?
Answer: We will start by removing the main suspense: the one-word answer is clearly, “Yes.” After seeing why, we will see why some prefer avoiding the situation and weigh certain factors and distinctions.
The gemara (Berachot 39b) says that on Shabbat, one needs to start the meals with two loaves of bread, based on the pasuk (Shemot 16:22) regarding the double portion of manna that fell in the desert. The gemara then says that Rav Kahana would hold two loaves [during the beracha] but only cut off bread from one of them. Rabbi Zeira, it continues, would cut into the “whole sheiruta.” Rashi (ad loc.) explains that this means that his first cut was enough challa for the whole meal. The Rashba (ad loc.) says that it means that R. Zeira would cut bread from each of the loaves.
It does not seem that the Rashba understood R. Zeira’s practice as being a halachic requisite, and in any case, the accepted opinion is that of Rashi, that the preference is to cut a big piece but of only one loaf (Rambam 7:3; Shulchan Aruch, Orach Chayim 274:1). Several Acharonim (see Yabia Omer, VIII, OC 32) understand that according to Rashi’s approach, only one loaf is there for eating, whereas the second one is just for a reminder of the miracle in the desert. Accordingly, the second one does not need to be fit to eat from a practical perspective.
There is a machloket whether we go as far as saying that it does not have to be ready to be eaten at all. For example, some say (see Tzitz Eliezer XIV:40) that one can even use matza for lechem mishneh on Erev Pesach even though one is not allowed to eat matza at that time. The Pri Megadim (MZ 274:2) suggests that even one who does not usually eat bread baked by a non-Jewish bakery could count it for the second loaf of lechem mishneh.
On the other hand, some poskim prefer not to use frozen challa for lechem mishneh. The Shevet Halevi (VI:31) opines that if there is an opinion that instructs to actually cut from both loaves then everyone agrees that it should at least to be fit to eat. The Shemirat Shabbat K’hilchata (55:(39)) cites Rav SZ Auerbach as saying that it is likely that it needs to be fit to eat at some type during the meal (the Shevet Halevi above seems to assume that the loaf would not be defrosted by meal’s end). Therefore, it seem that if one uses a pita or a roll, which will defrost within fifteen minutes or so, the consensus should be that it is totally fine.
One could ask that regarding a large loaf, as well, even if it takes more than an hour to defrost, the outer layer should defrost quicker, and the minimum size of a challa is only a k’zayit. The stringent leaning poskim probably assume that since people do not eat challa by peeling off the outside, the challa would have to be mainly defrosted (this distinction may be implicit in the Rambam, Shabbat 9:4).
Another distinction to consider is whether seuda shlishit is different from the other meals. In the direction of stringency, it is usually a shorter meal, therefore giving less time for defrosting, especially since for many it has a set finish time – before the standard time for Ma’ariv. It is even possible to argue that at that point of the day, if it does not count toward lechem mishneh, it is muktzeh. (The Tzitz Eliezer ibid. discusses this correlation, but says that it is fit for lechem mishneh and therefore not muktzeh; Mishneh Halachot XI:197 rejects the possibility of muktzeh). On the other hand, there is more room for leniency because it is unclear that lechem mishneh is needed at seuda shlishit (see Shulchan Aruch, OC 291:4-5).
In short, when there is a need, frozen lechem mishneh is valid, but there is some halachic logic to avoid it if it will not defrost during the meal. Yabia Omer (ibid.) said that it is preferable to borrow a challa from a neighbor and return it. Shemirat Shabbat K’hilchata (55:(43)) has a slight reservation whether it is considered fit for him to eat if he lacks permission to eat and not return it.