What happens if one misses a day? It is generally well known, that if one missed an entire day (the night and the subsequent day), the Shulchan Arukh states that one cannot continue to count with a berakhah. This ruling is based on the Ba’al Halakhot Gedolot, who views the entire sefira as a single unit. The individual days form a chain that constitutes a whole. Once this chain is broken, it is irreparable. Tosafos, however, take issue with this ruling. Clearly, in their opinion, we should not view the sefira in this way, but as series of separate, autonomous mitzvot that can be performed independently of one another.
The opinion of the Ba’al Halakhot Gedolot seems somewhat problematic. If indeed the sefira is essentially one mitzvah with 49 components, why do we make 49 blessings? Surely it is comparable to the mitzvah of searching for chametz, performed on the night of the 14th of Nissan, and the destroying of chametz, which occurs the following morning. In this case the mitzvoth are each part of one unit, and the berakah we make in the night, on the searching, covers the subsequent burning
Furthermore, according to the Ba’al Halakhot Gedolot, it would seem that if one counted an unbroken chain of 48 days, but forgot on the final night, all of his blessings would be in vain! Since forgetting a day is not an uncommon phenomenon, it would seem more appropriate to recite one blessing, after the performance of the entire mitzvah, on the 49th night, if one managed to complete the count fully. This would be comparable to the case of the blessing over the immersion in mikveh, where some authorities rule that the blessing takes place after immersion, because of concerns that the mitzvah may not be performed properly.
One answer given to explain the rational behind the ruling of the Ba’al Halakhot Gedolot, is that the blessing itself constitutes an integral part of the count. One who counts without a blessing, may not have ‘broken the chain’ of days, but his mitzvah is compromised. This would explain a textual variant of the blessing over the counting of the Omer, cited by the Chok Ya’akov:Blessed are You our G-d… Who has sanctified us with His commandments, and commanded us concerning the counting of the Omer, THAT TODAY IS THE…day of the Omer. The Hebrew prefix of the letter shin, links the count itself to the preceding blessing.
Another explanation offered to support the ruling of the Ba’al Halakhot Gedolot, is that the blessing made on a single count, is a blessing over a ‘half-measure’ of a mitzvah. In fact, there are authorities who rule that a ‘half mitzvah’, e.g. eating a half a kezayit of matzah on seder night, is meaningless. Others, however, believe that it does constitute a mitzvah, and that just as in forbidden matters, a ‘half-measure’ is prohibited according to the Torah, so too a ‘half-mitzvah’, counts as a measure of performance of the mitzvah, thus explaining the position of the Ba’al Halakhot Gedolot.
The ruling of the Shulchan Arukh is based on the principle that in a doubtful situation involving an obligation to recite rabbinic blessings, we are lenient and do not recite the blessing. It follows, however, that if one is unsure of whether or nor he made the blessing, one may nonetheless continue to recite with a blessing, as we apply another halakhic rule, namely, sfek sfeka lekula There are many practical ramifications of this dispute.