The Parameters of the Mitzvah of Sefiras Ha-Omer

There are two major machlekos rishonim that come up in discussions of the parameters of the mitzvah of sefiras ha-omer. The first machlokes is whether sefiras ha-omer is one mitzvah or 49 mitzvos. In this machlokes, Tosefos, the Rosh and the Shibbelei HaLeket hold that each night is its own mitzvah, while the Behag holds that the entire 49-day period constitutes one long mitzvah. The second machlokes is whether one can fulfill the mitzvah of sefirah during the daytime. In this machlokes, the Rambam and the Behag allow a person to count by day, while Tosefos and the Shibbelei HaLeket hold that if he does so, he is not yotzei (the Rosh advises him to count without a bracha). The popular practice is to be machmir in both machlekos individually by counting without a bracha, if necessary. The kula at the conjunction of the two (i.e., relying on a daytime counting to continue a 49-day count) is, at first glance, sefeik sefeika, but is also the result of either of the opposing combinations of shittos of Tosefos/Shibbelei HaLeket and the Behag.

Mori v'rabbi HaRav Shlomo Wahrman, in Oros HaPesach (78), suggests that the two machlekos are connected, based on a Meiri in Rosh HaShanah (6a). The Meiri explains the apparent contradiction between bal te'acheir (delaying the offering of a neder), in which he's oveir every day on which he is delinquent, and bal talin (delaying the consumption of said korban), in which he's oveir only once, by noting that for the latter issur, the time of the consumption of a korban is a single uninterrupted period, while for the former issur, the time for the offering of a korban is interrupted by the end of each day. Hence, while he's oveir on each new day on bal te'acheir when the issur becomes relevant again, the issur of bal talin never loses its relevancy, so that once he's oveir immediately following the deadline of the korban's consumption, he never incurs any additional violations.

So, too, the Behag holds that the permitted time for counting the omer is not interrupted by nightfall. Hence, it can be viewed as being one long mitzvah, whose interruption by a missed day breaks it up. Tosefos and the Shibbelei HaLeket, on the other hand, hold that there are 49 distinct periods for the performance of the mitzvah of sefiras ha-omer, and each is independent of the others.