[15] The issue of Hallel on Rosh Ĥodesh is elucidated in Arakhin 10b, Ta’anit 28b, Tosafot ad loc., and Tosafot Berakhot 14a. (There is another type of obligatory Hallel that is not recited due to the sanctity of a day, but rather in response to a salvation, like the Hallel that we recite on Ĥanuka. See below 4:6 and 11:8.)

Most Rishonim – including Behag, Ritz Gi’at, Raavad, Rabbeinu Tam, Rosh, and Ran – maintain that one should recite a berakha on this Hallel. Rav Hai Gaon, Rabbeinu Ĥananel, and Talmidei Rabbeinu Yona maintain that one should recite a berakha when reciting it with the congregation, but not in private. See Beit Yosef and sa 422:2. Indeed, as sa states, those living around Eretz Yisrael were accustomed to reciting it without a berakha, while those living in Spain would recite the berakha (Ran, Magid Mishneh). Rema 422:2 writes that it is customary to recite a berakha even when reciting Hallel alone, but that it is preferable to recite it with a minyan, in order to account for the opinion that one should only recite the berakha with the congregation.

Until recently, several Sephardic communities, including Moroccan, Tunisian, and Turkish Jews, followed the custom that the ĥazan recites the berakhot before and after Hallel aloud. The congregation answers, "Amen," thus fulfilling their obligation, while those praying privately omit the berakhot. This is also the opinion of R. Moshe Kalfon Ha-Kohen, av beit din of Djerba, in Brit Kehuna oĥ 200:5 and Sho’el Ve-nish’al 2:60; R. Ĥayim Palachi in Kaf Ha-ĥayim §33; Shalmei Ĥagiga, p. 224, Ĥesed La-alafim 422:2, Sha’ar Ha-mifkad, and Responsa Mikveh Ha-mayim 3:24. In his Tevu’ot Shemesh, oĥ 68, R. Shalom Messas determined that this is the halakha in practice, although he himself would recite the berakha in an undertone, along with the ĥazan. Every community should continue following its own custom.

When people from different ethnic groups pray together, even if the ĥazan’s custom is to omit the berakha, it is proper for one of the participants who usually recite the berakha to recite the berakha out loud on behalf of those who do not recite a berakha. This way, the congregants will satisfy the opinion of the many poskim who maintain that one must recite a berakha, and at the same time avoid the concern of reciting a berakha le-vatala (berakha in vain). (See Yeĥaveh Da’at 4:31, which expresses apprehension regarding answering "Amen" to this berakha, as it may be a berakha le-vatala. However, many authorities maintain that one need not worry about answering "Amen" to one who recites a berakha in accordance with his community’s custom, which is based on the opinion of prominent poskim. I also heard this from R. Mordechai Eliyahu.)

According to all opinions, one should try to recite Hallel with the congregation. Hence, it is better to recite it with a minyan before prayers than to say it alone afterward. This is the opinion of Rabbeinu Peretz, as cited in Beit Yosef 422:2. Many Aĥaronim quote this as well, as we stated above. According to Kaf Ha-ĥayim 422:38, one should not change the order of the prayers.