Over the last two days we have discussed the question of whether one may count the omer during the period of bein ha-shemashot – the period between sunset and nightfall – when it is uncertain whether or not the obligation of counting has already set in. Some Rishonim permitted counting during this period, as counting nowadays constitutes a rabbinic obligation, regarding which we may apply the principle of “safeik de-rabbanan le-hakel,” allowing us to rely on the lenient possibility in cases of uncertainty when a rabbinic provision is at stake. Others, however, maintained that this principle applies only after the fact, but does not allow us from the outset to knowingly place ourselves in a situation where we need to rely on one of two uncertain possibilities.
This debate likely revolves around the broader question as to the reason and nature of the principle of “safeik de-rabbanan le-hakel.” Conceivably, we could explain this rule in one of two ways. The simpler and more intuitive approach is that this rule reflects a lower level of severity. Violating a law enacted by our Sages is certainly a grave matter, by virtue of the authority which the Torah invests in them to enact provisions and safeguards, but it is less severe than transgressing a law introduced by the Torah itself. In cases of uncertainty, then, the stakes are lower, so-to-speak, when dealing with a rabbinic provision, and thus Halakha permits relying on the lenient possibility. If so, then it is certainly conceivable that the rule of “safeik de-rabbanan le-hakel” applies only after the fact. Although violating rabbinic ordinances is not as severe a religious offense as violating a Torah law, they certainly must not be treated lightly, and thus it stands to reason, or it is at least very possible, that one optimally ought to be stringent in situations of uncertainty even when a rabbinic law is at stake. It is only when a mistake was made that the rule of “safeik de-rabbanan le-hakel” allows for leniency.
A different approach, however, appears in a famous passage in the Ramban’s critique to the Rambam’s Sefer Ha-mitzvot. At the very beginning of the Sefer Ha-mitzvot, the Rambam asserts that all the laws enacted by Chazal must be obeyed by force of the Torah prohibition of “lo tassur” (Devarim 17:11), which forbids disobeying the nation’s leading body of rabbinic authority. The Ramban, in his critique, raises the question of why, according to this perspective, Halakha treats rabbinic laws differently from Biblical laws. If every rabbinic law must be obeyed by force of the Torah prohibition of “lo tassur,” then there should be no reason for greater leniency in situations of uncertainty regarding a rabbinic provision than in those involving Torah law. The Ramban suggests defending the Rambam’s position by postulating that Chazal from the outset enacted their provisions to apply only in situations of certainty. Meaning, the rule of “safeik de-rabbanan le-hakel” is based not on the lower level of severity of rabbinic enactments, but rather on the fact that Chazal initially intended for their rules to be followed only when they are definitively applicable. Thus, although transgressing a rabbinic law amounts to a violation of the Torah law of “lo tassur,” rabbinic laws are treated more leniently in situations of uncertainty because this is how they were formulated from the outset.
According to this understanding, it seems reasonable to assume that the rule of “safeik de-rabbanan le-hakel” applies even “le-khatechila” (optimally), and not just after the fact. If Chazal from the outset enacted their laws to apply only in situations of certainty, when they are definitively relevant, then in cases of uncertainty one need not be concerned at all with the law in question. This perspective, then, would likely underlie the view among the Rishonim permitting counting the omer during bein ha-shemashot, despite the uncertainty involved.
(See also Rav Asher Weiss’ extensive article on this topic.)