Biblical or Rabbinic: That is the Question

Tosfos concludes that the other restrictions, besides forbidden labor and eating, on Yom Kippur do not carry the penalty of kares, because they are only rabbinic. However, other Rishonim, such as the Rambam, disagree and are of the opinion that the other Yom Kippur restrictions are forbidden min HaTorah, only that the Torah specifically excludes them from the kares penalty.

The Mishna Berura notes that many Rishonim debate this issue, and it is unresolved. The Mishna Berura (611:3) concludes that as a matter of practical halacha, it is appropriate to act stringently. Of course, the restrictions are forbidden either biblically or rabbinically; what difference does it make to know the nature of the prohibition?

The Mishna Berura mentions two practical applications. The first is where one is forced to walk barefoot among goyim who are ridiculing him. If the prohibition to wear leather shoes on Yom Kippur was only rabbinic, we would permit him to wear leather shoes for the walk home. However, since it might be a Torah law, the Mishna Berura says one should not employ this heter.

The second practical difference between the two sides is in a situation of doubt. As a general rule (stated simplistically), when it comes to a doubt regarding Torah law, we must act stringently, safek de’Oraysah l’chumra. However, often when the doubt is regarding a rabbinic law, we rule leniently, safek de’rabbanan l’kula. Suppose one had a pair of shoes and there was a doubt whether they were made of leather or not. Further, there is no practical way to identify the material. According to Tosfos, one may wear the shoes on Yom Kippur, safek de’rabbanan l’kula. According to the Rambam, one may not wear the shoes on Yom Kippur, safek de’Oraysah l’chumra.

There are other areas of halacha where we have a similar doubt about whether something is m’de’rabbanan or min haTorah. When a man eats a bread meal and is satiated, he has a Torah obligation to bentch. Consequently, if he is unsure whether or not he bentched already, he must now bentch (assuming the time to do so has not passed.) because safek de’Oraysah l’chumra. The Gemara in Berachos (20) has a doubt about whether women have a Torah obligation to bentch. Perhaps only someone who is obligated in bris milah has a Torah obligation to bentch. The question is unresolved. Women certainly have at least a rabbinic obligation to bentch.

What should a woman do if she ate a satisfying bread meal and is unsure if she bentched already? Rebba Akiva Eiger suggests that she should not bentch now. He reasons that there is sfeik sfaika, a double doubt, that enables us to rule leniently. To follow his logic, one has to treat this question as a math problem with an order of operations. We must first discuss the question on a Torah level. Does a woman have an obligation to bentch? A) Yes; B) No

Viewed simplistically as a mathematical question, only fifty percent of the possible outcomes (A) indicate a woman has a Torah obligation to bentch. Even if a woman has a Torah obligation to bentch, perhaps she bentched already (C). But then again, maybe she didn’t (D). Once again, viewed simplistically as a mathematical question, 75% of the possible outcomes would indicate that this woman should not bentch now (BC, BD, AC). The only way the woman would have to bentch now on a Torah level is by assuming that, in general, she has a Torah obligation to bentch and she did not bentch already (AD). Since that is a minority outcome, Rebbe Akiva Eiger says we are not concerned with it. We generally follow the majority. Nevertheless, she definitely has a rabbinic obligation to bentch. However, since she is unsure whether or not she bentched, that is a question of a rabbinic obligation, and we rule safek de’rabbanan l’kula and she should not bentch now.

The Mishna Berura does not fully accept the logic and conclusion of Rebba Akiva Eiger. He says that a woman who finds herself in this situation and bentches out of doubt “does not lose.” Rebbe Shlomo Zalman, zt”l, more forcefully rejects Rebba Akiva Eiger’s conclusion when it comes to this situation. He rules that either a man or woman who ate a satisfying bread meal and is unsure if they bentched, should bentch now assuming the time has not yet elapsed. (That time is not less than 72 minutes.)

Rebbe Akiva Eiger’s logic could apply as well to the original question of a doubt regarding the permissibility of wearing a specific pair of shoes on Yom Kippur. However, the Mishna Berura does not cite it there. Still, perhaps that is why he concludes that it is only “appropriate to act stringently.” This is due to the fact that one who acts leniently has the opinion of Rebbe Akiva Eiger to rely on.