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D20. Determining Occurrence of the New Moon.    [Make a Comment]

We are to determine the occurrence of every new moon.

This precept is derived from His Word (blessed be He):

Key Scriptures

Exodus 12:2-3 (Maimonides RP153; Chinuch C4)
You are to begin your calendar with this month; it will be the first month of the year for you. Speak to all the assembly of Isra'el and say, 'On the tenth day of this month, each man is to take a lamb or kid for his family, one per household'

Exodus 13:10 (Maimonides RP153; Chinuch C4)
Therefore you are to observe this regulation at its proper time, year after year.

Exodus 34:22 (Chinuch C4)
Observe the festival of Shavu'ot with the first-gathered produce of the wheat harvest, and the festival of ingathering at the turn of the year.

Leviticus 23:4 (Maimonides RP153; Chinuch C4)
These are the designated times of ADONAI, the holy convocations you are to proclaim at their designated times.

Numbers 11:20 (Maimonides RP15)
... but a whole month! - until it comes out of your nose and you hate it! - because you have rejected ADONAI, who is here with you, and distressed him with your crying and asking, "Why did we ever leave Egypt?"

Numbers 11:21 (Chinuch C4)
But Moshe said, "Here I am with six hundred thousand men on foot, and yet you say, 'I will give them meat to eat for a whole month!'"

Numbers 28:11 (Maimonides RP42; Chinuch C403)
At each Rosh-Hodesh of yours, you are to present a burnt offering to ADONAI consisting of two young bulls, one ram and seven male lambs in their first year and without defect

Deuteronomy 16:1 (Maimonides RP153; Chinuch C4)
Observe the month of Aviv, and keep Pesach to ADONAI your God; for in the month of Aviv, ADONAI your God brought you out of Egypt at night.

Colossians 2:16
So don't let anyone pass judgment on you in connection with eating and drinking, or in regard to a Jewish festival or Rosh-Hodesh or Shabbat.


There is no explicit biblical commandment to determine the occurrence of the New Moon (Rosh Chodesh), but the numerous references to the beginning of months and to the New Year makes it a logical imperative to do so. Colossians 2:16 is the only mention of the New Moon in the Apostolic Writings, but there are several references in the New Testament to months and years.

The difficulty of determining the appearance of a New Moon is that there is no appearance of the moon at all. On the night of a New Moon, one sees no moon - similar to nights that are clouded over. During the time of Yeshua, the New Moon was declared by the San Hedrin upon its receiving the testimony of two individuals that they observed it. How can one see a moon that one cannot see? The testimony received was that the witnesses saw the last sliver of moon showing from the night previous.

Using modern astronomical methods of determining the New Moon is more precise and is acceptable in most of Judaism today. Explaining these methods is, however, beyond the scope of this Mitzvah.

Classical Commentators

Maimonides and HaChinuch reference the above Torah Scriptures to support their respective mitzvot regarding the New Moon. Meir is silent on the subject.


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