How did the Sanhedrin fulfill the sanctification commandment in practice?

By convening on the thirtieth day of each month to receive witnesses who had observed the new crescent moon, officially declaring Rosh Chodesh and transmitting the date to all of Israel.

Commandment #152 · Positive · Sabbath & Holy Days

This Month Shall Be Unto You: Sanctifying Rosh Chodesh

Q: Why is Exodus 12:2 significant as the first commandment addressed to Israel as a nation?

It establishes that Israel's identity begins not with a law about ethics or ritual but with authority over time -- the ability to declare and structure the calendar around redemption.

Q: What does Rashi's observation that the Torah could have begun with Exodus 12:2 suggest?

That the entire Torah -- from Creation onward -- is in some sense the backstory to the Exodus, making the command to sanctify the Exodus month the Torah's true starting point.

Q: Why does the Exodus month becoming the 'first month' re-order all of Israel's time?

Because it subordinates the natural agricultural calendar to the calendar of redemption -- Israel marks time from what God did, not from what the seasons do.

Q: How do Numbers 28:11's additional monthly offerings express the ongoing significance of Rosh Chodesh?

By requiring special burnt offerings at each new month, the Torah builds a recurring ceremonial acknowledgment of the sanctified-time structure established in Exodus 12:2.

קִדּוּשׁ הַחֹדֶשׁ

Source: Exodus 12:2 · Maimonides, Sefer HaMitzvot, Positive #153

Exodus 12:2 is the first commandment given to Israel as a nation — and it is not about ethics or ritual: it is about time. 'This month shall be unto you the beginning of months: it shall be the first month of the year to you.' Before the final plague, before the Exodus itself, God redesigned Israel's calendar around the act of redemption. Numbers 28:11's additional offerings at each new month, and the Sanhedrin's monthly court session to receive moon-witnesses, both flow from this single verse's mandate.

This Month Shall Be the Beginning of Months

הַחֹדֶשׁ הַזֶּה לָכֶם רֹאשׁ חֳדָשִׁים רִאשׁוֹן הוּא לָכֶם לְחָדְשֵׁי הַשָּׁנָה

"This month shall be unto you the beginning of months: it shall be the first month of the year to you."

Exodus 12:2 — Open in Torah Reader

Exodus 12:2 is the first commandment addressed to Israel as a nation. Before the plagues end, before the Exodus itself, God instructs Moses and Aaron to fix the month of the departure as the head of months. Rashi notes that the Torah could have begun with this verse rather than with Creation — the entire Torah being, in one sense, the working-out of this single act of redemption that reshaped Israel's time.

The command to 'sanctify' the new month — Kiddush HaChodesh — was fulfilled in practice by the Sanhedrin receiving witnesses who had observed the new crescent moon. Only after the court officially declared the new month did the calendar for that month become authoritative, fixing the dates of Sabbaths, festivals, and months for all of Israel. Numbers 28:11 ties special Rosh Chodesh offerings to this monthly recognition.

In the First Month of the Year

וּבְרָאשֵׁי חָדְשֵׁיכֶם תַּקְרִיבוּ עֹלָה לַיהוָה

"And in the beginnings of your months ye shall offer a burnt offering unto the LORD."

Numbers 28:11 — Open in Torah Reader

Numbers 28:11 prescribes the Rosh Chodesh musaf — additional burnt offerings presented specifically at the beginning of each new month. The festival structure of Leviticus 23 is built around months whose official start depends on this commandment. Every Passover, every Shavuot date, every Day of Atonement depends on the court's correct declaration of the new month.

The Exodus month (Exodus 12:2) became the first month precisely because that is when God acted. Israel's sacred calendar does not follow the rhythm of harvests or planetary cycles as its ultimate authority — it follows the rhythm of redemption. The court's monthly declaration was therefore not administrative but theological: it re-enacted Israel's authority, given at Sinai, to structure time around the acts of God.

Key Figures

Moses and Aaron

The commandment at Exod 12:2 is addressed to 'Moses and Aaron' together — the beginning of the priestly-prophetic partnership that would govern Israel's calendar. Every subsequent Rosh Chodesh declaration by the Sanhedrin traces its authority back to this joint commission.

The Great Sanhedrin

Just as Commandment #141 established Israel's supreme court for legal decisions, that same court held exclusive authority over the calendar. Witnesses would appear before the Sanhedrin on the thirtieth day; if they confirmed the new crescent, the court declared Rosh Chodesh and sent fire-signals across the land.

Study Questions

For reflection and group study

Why is Exodus 12:2 significant as the first commandment addressed to Israel as a nation?

What does Rashi's observation — that the Torah could have begun with Exodus 12:2 — imply about the relationship between Creation and the Exodus?

How did the Sanhedrin's role in receiving new-moon witnesses connect the judicial system to Israel's sacred calendar?

In what sense does the Exodus month becoming the 'first month' re-order all of Israel's time around an act of redemption rather than nature?

How do Numbers 28:11's additional monthly offerings express the ongoing significance of the new-month sanctification?

Read the full passage on the new month sanctification in the Torah reader.

Open Exodus 12 in the Bible Reader

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