Halacha Date: 12 Av 5778 July 24 2018
Answer: We have been asked this question several times recently and thus, let us now explain this matter.
Women are obligated to pray one prayer daily, as we have explained in the Halacha regarding a woman’s obligation to recite the Amida prayer. (Although there are some Ashkenazi Poskim who rule that women are obligated to pray Shacharit and Mincha daily, according to Maran Ha’Shulchan Aruch this is not the case and they are obligated to pray only once a day.) According to many Rishonim, the primary reason why women are obligated to pray once a day is because prayer is a request for mercy from Hashem regarding all of our needs; since women are also in need of Hashem’s mercy, they are thus also required to pray according to the letter of the law. This is also the root of the question regarding a woman praying Mussaf, for the Mussaf prayer is not meant as a plea for Hashem’s mercy and is also a positive, time-bound Mitzvah (for Mussaf is only recited on Shabbat and not on the other days of the week). It therefore seems that women should be exempt from this prayer. Indeed, Hagaon Rabbi Akiva Eiger in his responsa (Chapter 9) writes that since the Mussaf prayer was established instead of the Mussaf offering which was brought only by men and not by women, it therefore seems that they are not included in the obligation to pray Mussaf.
Since it seems that women are exempt from reciting the Mussaf prayer on Shabbat, Maran Rabbeinu Ovadia Yosef zt”l writes in his Responsa Yabia Omer (Volume 2, Chapter 6) that according to Maran Ha’Shulchan Aruch who rules that women may not recite a blessing when performing a positive, time-bound Mitzvah, such as Lulav and Sukkah, they should likewise not pray Mussaf at all since Mussaf, which was instituted in lieu of the Mussaf offering, does not pertain to women so much in addition to the fact that it is a positive, time-bound Mitzvah from which women are exempt. Thus, even if they wish to, women should not recite the Mussaf prayer out of concern for uttering several blessings in vain.
Nevertheless, Maran zt”l writes in his newer Chazon Ovadia-Shabbat, Volume 2 (page 204), which was published in Maran zt”l’s later years, that many great Acharonim rebuff the claim that Mussaf does not pertain to women including the great Amudei Ohr who writes that although women would not bring the Mussaf offering, they would nevertheless receive atonement as a result of it just like men. A proof to this claim is that although the Mussaf offering did not relate to the Levi’im (Levites), they would nevertheless pray Mussaf (as the Gemara says that Rabbi Yehoshua ben Levi, who was a Levi, would indeed pray Mussaf). This proves that even those who did not bring the Mussaf offering are still included in it because of the atonement they would achieve as a result of it and by default, they may pray Mussaf. The same would apply to women and they would be permitted to pray Mussaf.
Regarding what we have written that Mussaf is a positive, time-bound Mitzvah which women are exempt from performing, Maran Rabbeinu zt”l rejects this claim by saying that since according several Rishonim, if a Mitzvah is of rabbinic origin and not a Torah law, even women are commanded to perform it. Thus, Mussaf is certainly a rabbinic enactment and we therefore cannot say that women are not permitted to recite it. This is especially true since several great Acharonim attest to the fact that the custom was for women to indeed pray Mussaf.
Based on the above, Maran zt”l rules that any woman of valor who wishes to pray Mussaf on Shabbat may in fact do so.