Reprinted with permission of the Schechter Institute of Jewish Studies.
The ritual known today as birkat hachodesh, “the blessing of the new moon,” is widely observed in synagogues throughout the world. On the last Shabbat of the Hebrew month, the cantor stands with the Torah scroll in his arms, and announces the day of the coming week on which the New Moon, Rosh Chodesh, will fall. The announcement is preceded and followed by particularly melodious prayers for a blessed month.
This ritual is a post-Talmudic custom with little halakhic [Jewish law] significance. Its purpose is to make sure that those members of the congregation who attended synagogue services on Shabbat only would know when this minor festival falls, so that they could add the appropriate supplements in their home prayers (Shibbolei Haleket 170).
A similar announcement is made in Sephardic synagogues on the Shabbat before a minor fast, out of concern that otherwise the congregants will not remember to. The announcement of the New Moon, far from signifying the importance of the Rosh Chodesh festival, in effect reflects a fear that the festival is not significant enough to be remembered and observed.
However, the very same term, “birkat hachodesh,” is used in the Talmud to designate a very different ritual–a blessing praising God for the new moon, recited outdoors while gazing at the waxing moon at the beginning of the month (Sanhedrin 41b). This ritual, with which many Jews, even those who attend synagogue services regularly, are unfamiliar, is an actual rabbinic commandment, required by the Talmud.
The Shulhan Arukh (Orah Hayyim 426) and other post-Talmudic authorities refer to this ritual as birkat halevanah, “the blessing of the moon,” but today it is often designated by the misnomer kiddush levanah, “the sanctification of the moon,” a term that sounds almost pagan. (This phrase is apparently a conflation of the term birkat halevanah with the talmudic term kiddush hachodesh, “the sanctification of the new moon,” which referred to yet a third concept, the proclamation of the New Moon by the authorities on the day of its sighting, an act by which Israel did in fact sanctify the dates of the holidays that are dependent upon the lunar month.)