Rosh Chodesh

Rosh Ĥodesh is a time of atonement. In order to make this atonement complete, pious Jews customarily repent in for the time leading up to Rosh Ĥodesh. Some people fast on the day before Rosh Ĥodesh and recite special Yom Kippur Katan prayers prior to the Minĥa service.

On the Shabbat preceding Rosh Ĥodesh (known as Shabbat Mevarkhim), it is customary to announce when Rosh Ĥodesh will take place and recite Birkat Ha-ĥodesh (“blessing the new month”), a prayer that God “renew this month for us and for all His people, the house of Israel, for good and blessing.”

One may work on Rosh Ĥodesh. Ideally, though, one should not do so, as is the law on Ĥol Ha-mo’ed. The rule is that the holier the day, the more it is designated for holy endeavors, and the more one should limit his involvement in work.

The Torah lists Rosh Ĥodesh together with all the other festivals on which we bring Musafim (additional offerings) in honor of the day’s sanctity.

Rosh Hodesh is one of the holidays on which it is appropriate to rejoice. However, there is no explicit commandment to rejoice on Rosh Ĥodesh by conducting festive meals.

When a month is incomplete (29 days), the following Rosh Ĥodesh is observed for one day. When it is full (thirty days), the following Rosh Ĥodesh lasts two days: the thirtieth day of the previous month and the first day of the next month.

The Sages of Eretz Yisrael retained the authority to sanctify months and intercalate years, as it says, “For Torah shall come forth from Zion”.

A new month does not automatically begin when the moon reappears. Rather, the beit din sanctifies the month, as it says, “This month shall mark for you”.

Read the laws of Rosh Ĥodesh from "Peninei Halakha"