It is customary to announce Rosh Hodesh during the prayer service on the Shabbat before Rosh Hodesh in the synagogue. Thus, for example, when Rosh Hodesh Elul falls on Tuesday and Wednesday (as it did this year), an announcement would be made to this effect in the synagogue on the preceding Shabbat. The announcement is recited along with a special Yehi Rason prayer. The announcement is made on Shabbat for the simple reason that Shabbat is when a large crowd assembles in the synagogue, thus offering the best opportunity to inform the congregation of the onset of Rosh Hodesh.
Among the things we pray for in the Yehi Rason prayer is "Le’kayem Lanu Hachmeh Yisrael" – the wellbeing of the Rabbis and their families. The reason why this is mentioned as part of the Rosh Hodesh declaration is because in ancient times, the declaration of the new month was dependent upon the decision of the Hachamim. Witnesses who saw the new moon would testify to this effect before the Rabbinical Court in Jerusalem, and the Rabbis would then declare, "Mekudash, Mekudash, Mekudash," proclaiming the onset of the new month. Therefore, in light of the vital role played by the Hachamim in the process of proclaiming a new month, we offer a prayer for them when we announce Rosh Hodesh in the synagogue.
During this declaration we also make mention of the Exodus from Egypt ("Mi She’asa Nissim La’abotenu U’mi’Misrayim Ge’alam"), in commemoration of the very first declaration of Rosh Hodesh, which took place at the time of the Exodus ("Ha’hodesh Ha’zeh Lachem Rosh Hodashim" – Shemot 12:2).
The Kaf Ha’haim (Rav Yaakob Haim Sofer, Baghdad-Israel, 1870-1939) records the custom to stand during the announcement of the new month. Many communities follow this practice, though this is not the custom in the Syrian Jewish community.
There is another custom observed by many communities (especially among Lebanese Jews) to go up to the Teba and hold onto the Sefer Torah during the announcement of Rosh Hodesh. Many people are unaware of the reason behind this custom, which has to do with a ruling in the Gemara, in Masechet Rosh Hashanah, concerning the Rosh Hodesh declaration. The Pasuk says (Vayikra 23:2), "Eleh Mo’adeh Hashem Asher Tikre’u Otam" ("These are the special occasions of Hashem which you shall declare"), and the Gemara comments that the word "Otam" should be read as "Atem" ("you"), as if to say, "Atem Afilu Mut’in." This means that even if the Hachamim make a mistake and miscalculate the onset of the new month, Hashem accepts their mistaken proclamation. If they are off by a day, Hashem nevertheless accepts their decision and adjusts the entire calendar accordingly, such that Pesah, for example, will begin a day earlier and end a day earlier, thus allowing people to eat Hametz on the day that was to have been the final day of Pesah. The closest representation of the Almighty that we have in the synagogue is the Sefer Torah, because, as the Zohar comments, "Israel, the Torah and the Almighty are one." And thus during the announcement of Rosh Hodesh, some communities have the custom to grab onto the Torah symbolizing G-d’s inclusion in this process, as He accepts and follows our Sages’ declaration of Rosh Hodesh.
It is customary not to announce the month of Tishri on the Shabbat before Rosh Hashanah, because the Pasuk (Tehillim 81:4) states about this month, "Ba’kese Le’yom Hagenu," indicating that this month should be "concealed," without a public announcement. When announcing the month of Heshvan, we use the name "Marheshvan," which is the month’s real name. Different customs exist regarding the announcement of Rosh Hodesh Ab, as some communities refer to the month by its actual name, Ab, whereas other call it "Menahem Ab," despite the fact that "Menahem" is not actually part of the name. (And thus, for example, if a Rabbi writes a Get during the month of Ab, he writes only "Ab" and not "Menahem Ab.") When announcing the onset of the month of Adar during a leap year, we recite either "Adar Rishon" or "Adar Sheni." Some communities have the custom when announcing Rosh Hodesh Elul to refer to the month as "Elul Rahamim." Although "Rahamim" is clearly not part of the month’s name, they nevertheless add this word to remind the congregation that Elul is a special time of divine mercy and compassion, during which we must all strive to perform proper Teshuba.
