At first glance, the notion that we can raise an optional mitzvah to the level of obligation is anathema, even heretical. We are familiar with the prohibition of bal tosif, which dictates that an individual may not add a mitzvah beyond the 613 legislated by the Torah. Yet, with regard to the recitation of Al Hanissim on Chanukka, we seem to do just this!
The Gemara (Shabbat 24a) inquires as to whether one is obligated to insert Al Hanissim in birchat hamazon. The Gemara concludes that the addition of Al Hanissim during bentching is optional.
On the basis of the Gemara’s conclusion, numerous medieval authorities including Tosafot (ibid. s.v. de-tani) extrapolate that one who omits Al Hanissim need not repeat Shemoneh Esrei. Furthermore, these rishonim support this contention on the basis of a Tosefta (Berachot Chapter 4), which explicitly rules that on holidays on which mussaf is not recited, one who omits that holiday’s addition to Shemoneh Esrei need not repeat the Amidah.
In light of the above evidence, one position among the rishonim emerges as quite unusual. Ra’avya (2:563, cited by Mordechai Shabbat 2:279) rules that since we have accepted the recitation of Al Hanissim upon ourselves as mandatory, one who neglects its recitation must repeat Shemoneh Esrei! Ra’avya (2:566, cited by Beit Yosef O.C. 188) echoes this same essential position in another context: although some maintain that one is not obligated to eat bread at seudah shelishit on Shabbat, nevertheless one who does so regularly has obligated himself in the recitation of birchat ha-mazon, and must therefore repeat bentching if he were to omit Retzei.
In both instances, Al Hanissim and Retzei, Beit Yosef (O.C. 188, 682) vigorously rejects Ra’avya’s chiddush, arguing that even one who has accepted the recitation of Al Hanissim or Retzei as obligatory need not repeat Shemoneh Esrei or birchat hamazon due to such an omission.
What is the underlying difference of opinion between Beit Yosef and Mordechai? It would appear that for Beit Yosef, accepting optional practice as mandatory is merely a function of the category of neder, one’s vow or ability to accept a requirement upon oneself. One who omits Al Hanissim or Retzei has erred, but need not repeat – and indeed would not be permitted to repeat, with the exception of a voluntary additional prayer – Shemoneh Esrei. For Ra’avya, however, the notion of personal practice cuts much deeper: by accepting the recitation of Al Hanissim as mandatory, one transforms that prayer from an extrinsic add-on to an intrinsic component of Shemoneh Esrei. Therefore, one who omits Al Hanissim or Retzei must repeat the entire recitation, as the tefilla or birchat hamazon is fundamentally incomplete.
Ra’avya, then, is articulating a remarkable chiddush: to some degree, we have the ability to raise an optional mitzvah to the level of obligation. This implies a far-reaching claim about the human role in the halakhic system: God not only legislates and asks the Rabbis to enact decrees, but individuals or communities as well, in limited circumstances, have the ability to add additional dimensions to halakha.
This theme of limited but meaningful innovation is apropos to Chanukka. The very right of our Rabbis to institute a new holiday, as well as the ability of the individual to choose among the various levels of the base mitzvah of lighting the Menorah, mehadrin, and mehadrin min hamehadrin, all contribute to the notion that God desires that humans not only obey His laws but also partner with Him in the unfolding of the tradition. By embracing the mitzvot of Chanuka, may we merit not only to follow the mandates of halakha but also to partner with the Almighty in manifesting His will on earth.