A Siyum Validates It
‘Thereupon The Decrees Were Annulled’
(Ta’anis 18a)
The Gemara relates that the Romans once issued a decree prohibiting Jews from studying Torah and performing mitzvos. Eventually, the Jews succeeded in having the ban lifted and, in gratitude to Hashem, they declared that day a Yom Tov (when fasting and eulogizing is forbidden). This Yom Tov was similar to many other days mentioned in Megillas Ta’anis on which fasting and eulogizing were forbidden due to joyous events that occurred on those dates. No New Festivals
Halacha l’maaseh follows the opinion that after the destruction of the Beis Hamikdash, the Yamim Tovim mentioned in Megillas Ta’anis were discontinued.
The Gemara (Rosh Hashanah 18b) asserts that if Jews ceased observing all the previously established rabbinic Yamim Tovim after the churban (except for Chanukah and Purim), they certainly took it upon themselves not to establish any new Yamim Tovim henceforth.
Discretionary Feasts
Based on this Gemara, the PriChadash (Orach Chayim 496, Kuntress Haminhagim 14) asserts that the festival days declared by certain communities in celebration of being saved from danger are not binding on their members. The feasts eaten on these festive days (called “Purim” in certain communities) are considered merely seudos reshus (discretionary feasts), not seudos mitzvah.
The Maharam Alshekar, however (cited by MagenAvraham, Orach Chayim 686:sk5), argues that a community can establish a celebratory feast that is binding on all those living at that time, plus future generations.
The Chasam Sofer’s View
The ChasamSofer (Responsum Orach Chayim 191, 163) cites our Gemara – about the holiday declared after the Romans lifted their ban on studying Torah and observing mitzvos – as proof that Yamim Tovim were established even after the churban.
He argues that when the Gemara in Rosh Hashanah states that we no longer establish new festivals after the churban, it refers only to national festivals, not to festivals celebrated by individual communities.
A Familial Miracle
The ChayeiAdam (155:41) also makes this distinction and rules that it is a mitzvah for a community or family to make a feast of thanksgiving on the anniversary of a miraculous deliverance that occurred to them. To this end he cites the Maharshal (Yam Shel Shlomo to Bava Kamma, siman 37), who writes that a feast made for the sake of remembering and reflecting on the wondrous and miraculous ways of Hashem is a seudas mitzvah.
The Chayei Adam also asserts that the PriChadash would have agreed with the view of Maharshal had Yam Shel Shlomo been printed in his time.
In A New Community
The ChasamSofer (op. cit.) concludes that it is a mitzvah for a community to make a celebration on the anniversary of a miraculous deliverance that occurred to them. He cites the YosefOmetz, who relates that the 20th of Adar was celebrated as a festival in Frankfurt because of a miracle that occurred to the community on that date. He relates that his teacher, R. Nathan Adler of Frankfurt, continued celebrating on this day even after he left Frankfurt and moved elsewhere (in accordance with the view of MaharamAlshekar).
The ChasamSofer writes that he, too, continued to celebrate the 20th of Adar after he moved to Hungary. However, in order to ensure that the special meal he ate that day was a seudas mitzvah according to all opinions, the Chasam Sofer would complete a masechta on that day and make a siyum.