And the LORD spoke unto Moses, saying: ’And I, behold, I have taken the Levites from among the children of Israel instead of every first-born that openeth the womb among the children of Israel; and the Levites shall be Mine; for all the first-born are Mine: on the day that I smote all the first-born in the land of Egypt I hallowed unto Me all the first-born in Israel, both man and beast, Mine they shall be: I am the LORD.’

All that were numbered of the Levites, whom Moses … all the males from a month old and upward, were twenty and two thousand. (Numbers 3:11–13, 39 (with omissions))

וַיְדַבֵּר ה' אֶל מֹשֶׁה לֵּאמֹר. וַאֲנִי הִנֵּה לָקַחְתִּי אֶת הַלְוִיִּם מִתּוֹךְ בְּנֵי יִשְׂרָאֵל תַּחַת כָּל בְּכוֹר פֶּטֶר רֶחֶם מִבְּנֵי יִשְׂרָאֵל – וְהָיוּ לִי הַלְוִיִּם. כִּי לִי כָּל בְּכוֹר, בְּיוֹם הַכֹּתִי כָל בְּכוֹר בְּאֶרֶץ מִצְרַיִם, הִקְדַּשְׁתִּי לִי כָל בְּכוֹר בְּיִשְׂרָאֵל, מֵאָדָם עַד בְּהֵמָה – לִי יִהְיוּ, אֲנִי ה'.

כָּל פְּקוּדֵי הַלְוִיִּם, אֲשֶׁר פָּקַד מֹשֶׁה ... כָּל זָכָר, מִבֶּן חֹדֶשׁ וָמַעְלָה: שְׁנַיִם וְעֶשְׂרִים אָלֶף.

And all the first-born males according to the number of names, from a month old and upward, of those that were numbered of them, were twenty and two thousand two hundred and threescore and thirteen. (Numbers 3:43)

וַיְהִי כָל בְּכוֹר זָכָר, בְּמִסְפַּר שֵׁמוֹת, מִבֶּן חֹדֶשׁ וָמַעְלָה, לִפְקֻדֵיהֶם: שְׁנַיִם וְעֶשְׂרִים אֶלֶף שְׁלֹשָׁה וְשִׁבְעִים וּמָאתָיִם.

And the LORD spoke unto Moses, saying: ’Take the Levites instead of all the first-born among the children of Israel, … And as for the redemption of the two hundred and three score and thirteen of the first-born of the children of Israel, that are over and above the number of the Levites, thou shalt take five shekels apiece by the poll; … And thou shalt give the money wherewith they that remain over of them are redeemed unto Aaron and to his sons.’ (Numbers 3:44–48 (with omissions))

וַיְדַבֵּר ה' אֶל מֹשֶׁה לֵּאמֹר: קַח אֶת הַלְוִיִּם תַּחַת כָּל בְּכוֹר בִּבְנֵי יִשְׂרָאֵל ... וְאֵת פְּדוּיֵי הַשְּׁלֹשָׁה וְהַשִּׁבְעִים וְהַמָּאתָיִם, הָעֹדְפִים עַל הַלְוִיִּם מִבְּכוֹר בְּנֵי יִשְׂרָאֵל, וְלָקַחְתָּ חֲמֵשֶׁת חֲמֵשֶׁת שְׁקָלִים לַגֻּלְגֹּלֶת ... וְנָתַתָּה הַכֶּסֶף לְאַהֲרֹן וּלְבָנָיו, פְּדוּיֵי הָעֹדְפִים בָּהֶם. (במדבר ג׳, יא–יג, לט, מג–מח (בדילוג))

In Bamidbar, the Torah describes the substitution of the Levites for Israel’s firstborn. Moses was commanded to count the Levites from one month upward: they numbered 22,000. Israel’s firstborn were then counted from one month upward, reaching 22,273. The 273 surplus firstborn were redeemed at five shekels each.

At first sight, 22,273 poses no particular difficulty. If the count includes every firstborn of the womb, however – every first son ever born to his mother – a real difficulty arises.

Israel’s wilderness population is commonly put at approximately three million: six hundred thousand men of military age, a similar number of women of those ages, elderly people beyond military age, and children and youths under twenty, who formed the majority in a young, rapidly growing population.

To understand 22,273, remember that the number of firstborn lets us infer the actual number of mothers. Only male firstborn are counted; adding female firstborn yields approximately 44,000 first births. We must also add first births ending in miscarriage or death at birth, absent from the count. Even cautiously assuming a similar number of these yields about 88,000 mothers. This is extremely low relative to a population of millions. It implies that most adult women were not mothers at all, while the minority who did give birth had to bear dozens of children to produce such a population – a conclusion very hard to reconcile with reality.

Another possibility is that the count includes firstborn born since the exodus. Since the census occurred approximately a year after the departure, these would be firstborn born in that first year. Nahmanides mentions this possibility but rejects it:

What seems to me is that all these firstborn were not born in the wilderness in a single year, for the people did not multiply there to such an extent. (Nahmanides, Numbers 3:45)

והנראה אלי: כי הבכורים האלה כולם לא נולדו במדבר בשנה אחת, כי לא נתרבו העם שם כל כך" (רמב״ן, במדבר ג', מה).

Indeed, in a population of roughly three million, the male firstborn born in one year could number at most a few thousand. Only a small fraction of births are first births, only half are male, and miscarriages must be considered. There is therefore no way to reach 22,273 firstborn in a single year.

I propose a different understanding: the count includes neither all firstborn ever born nor only those born in the past year, but young firstborn, from one month to five years old.

This proposal rests first and foremost on the wording. The verse concerning redemption of the firstborn says:

And their redemption-money–from a month old shalt thou redeem them–shall be, according to thy valuation, five shekels of silver (Numbers 18:16)

וּפְדוּיָו מִבֶּן חֹדֶשׁ תִּפְדֶּה בְּעֶרְכְּךָ כֶּסֶף חֲמֵשֶׁת שְׁקָלִים (במדבר י"ח, טז).

“According to thy valuation” refers to the valuation passage at the end of Leviticus, where a male aged one month to five years is valued at five shekels (Leviticus 27:6). Redemption is thus not a fixed sum for any firstborn regardless of circumstances, but derives from his age. Had older firstborn been included, they would apparently have needed redemption according to their valuations – twenty, thirty, or fifty shekels – rather than a uniform five shekels. Hence the firstborn counted and redeemed were only one month to five years old.

This also fits the demographic scale: approximately 22,000 firstborn suits a limited group of young children up to five, rather than all firstborn, a larger number, or one year’s births, a smaller number.

The meaning of “for all the first-born are Mine” (Numbers 3:13) also becomes clear. It refers not to every person born firstborn, but to a defined group of young children up to five, still directly connected with “opening the womb.” Afterward, this connection expires, and the firstborn no longer falls within the sanctity of firstborn status that requires redemption.

This distinction also casts new light on the plague of the firstborn. It did not strike every adult born firstborn, but specifically this young age group of whom it says, “for all the first-born are Mine.”

A hint appears in the account preceding Egypt’s plagues (Exodus 4:21–26). Immediately after the LORD commands Moses to threaten Pharaoh – “behold, I will slay thy son, thy first-born” – we hear of Moses’ firstborn son, whom the LORD almost kills. This juxtaposition is not accidental: it indicates that the firstborn status in question is directly connected with opening the womb, a young child, rather than an adult for whom being the first to open the womb is merely a biographical fact.

One question remains: why does Israel’s firstborn count also say “from a month old and upward,” if it means only up to five?

The Torah apparently sought a verbal parallel between Israel’s firstborn census and the Levites’ census, and therefore used the same wording. But just as the military census says “from twenty years old and upward” while meaning up to sixty, so here: “from a month old and upward” is not an open-ended range but a defined one, corresponding to the age divisions in Leviticus’s valuation passage, namely up to five years.