Q. I have some more questions. Is it true that the Ramban maintains that women have to count the omer? Should one try to also follow his opinion?
A. Indeed the Ramban (Kiddushin 34a) rules that women are obligated to count Sefirat Ha’Omer. The Avnei Nezer (OH 384) explains the Ramban’s justification for his position is that the Torah writes that Sefira begins mi’mocharas HaShabbos, the second day of Pesach. Since Sefira is connected and linked to Pesach and women are obligated in many of those mitzvos, they are obligated in Sefira as well.
However most poskim do not accept the position of the Ramban and they rule that women are not obligated in this mitzvah. Yet the Magen Avrohom (O.H. 489:1) writes that women have accepted this mitzvah upon themselves, and it now has the status of an obligation. However, not all Acharonim accept this ruling, and indeed the Mishnah Berurah (489:3) writes that in his community it was not the custom for women to count Sefira.
Practically speaking, there is a wide range of customs. Some women count Sefiras Ha’Omer with a bracha, others count without a bracha or have someone else recite the bracha for them, and some do not count at all.
The dispute over whether Sefirat HaOmer today is a Biblical or rabbinic obligation has various ramifications, most importantly as we mentioned: What is the Halacha if there is a safek (uncertainty) if one counted? If this mitzvah is Biblical, we follow the rule that safek dioraisa lichumra (we are stringent), while if it is only Rabbinic, we are lenient since safek derabbanan likulah prevails.
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Rabbi A. Bartfeld as revised by Horav Hirshman, Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a.