On Chanuka (and Purim), we add the special Al HaNissim prayer in the Amidah and Birkat HaMazon. We don’t, however, make any mention of Chanuka (or Purim) in the bracha of Al HaMichya (etc). Why not?
This question bothered me for a long time.
In his excellent and highly readable new book, “Hilkhot Mo’adim – Understanding the Laws of the Festivals” (Maggid Books, 2013), R. David Brofsky gives two interesting explanations. The first is suggested by the Levush, R. Mordechai Yoffe, in his commentary on the Shulchan Aruch. Fundamentally, the Levush explains, Al HaNissim is a prayer of thanksgiving, and we therefore insert it in the brachot of thanksgiving in the Amidah (after Modim) and in Birkat HaMazon (after Node Lecha). In contrast, the bracha of Al HaMichya does not contain a section dedicated to thanking Hashem, and therefore Al HaNissim is simply thematically inconsistent with Al HaMichya.
R. Yosef Dov Soloveitchik offers a different explanation, which I once heard also from Dayan C. Ehrentreu in England. Retzei and Ya’ale ve’Yavo are not mere insertions into the text of Birkat HaMazon. They are an integral part of Birkat HaMazon and independent brachot. Proof of this can be found in the special brachot one adds if, when saying Birkat HaMazon, he forgets to say Retzei (asher natan Shabbatot li’menucha…) or Ya’ale ve’Yavo (asher natan Rashei Chodashim…), that express the same idea. The fact that the omission of Retzei and Ya’ale ve’Yavo warrants a special bracha and requires one to repeat the Amidah indicates that they are not mere insertions, but rather independent prayers! The omission of Al HaNissim, on the other hand, does not necessitate the repetition of the Amidah or Birkat HaMazon. This explains why Chanuka or Purim are not mentioned in Al HaMichya – as Al HaNissim is not essential enough to warrant repetition or the insertion of a separate bracha if it is omitted.
Why, though, did Chazal establish Retzei and Ya’ale ve’Yavo as independent brachot, while Al HaNissim is regarded as a mere insertion within a bracha? R. Soloveitchik explains that the difference lies in the formal holiness of the day – kedushat ha’yom – with which Shabbat and Yom Tov are endowed. This special status mandates inserting a separate and independent prayer mentioning these days in the Amidah and Birkat HaMazon. By contrast, Chanuka and Purim do not have kedushat ha’yom.