1. The Torah’s Law of the Bekhoir
In Parshas Ki Seitzei, the Torah discusses the unique privileges of a bekhoir—firstborn son. The verse describes a scenario where a man has two wives, one whom he loves and one whom he dislikes. Even if the firstborn is from the wife he likes less, he is still obligated to give that son the rights of the bekhoir. He cannot deprive the true firstborn of his status, regardless of his feelings toward the mother.
This law applies when both women are having their first child with this man. The bekhoir is determined by which child is born to him first, irrespective of which wife it is. If one wife has not yet had children, but the other gives birth first, her son is the bekhoir.
2. Defining Bekhoir: The Role of Petarechem
The situation becomes more complex if the woman was previously married and already had a child, or even if she had a miscarriage before this birth. In such cases, although it may be the husband’s first child, it is not the mother’s first pregnancy. The Torah specifies that bekhoir status depends on petarechem—the opening of the womb. This means that only a child who is his mother’s firstborn qualifies as a bekhoir, even for purposes relating to his father.
If the mother already had another child, then her next son cannot be considered a bekhoir, even if it is her new husband’s first child. Thus, bekhoir status hinges on being both the father’s and mother’s firstborn—specifically, her first live birth.
3. Contrast with Kohen and Levi Status
This requirement for petarechem stands in contrast to how we determine whether someone is a Kohen, Levi, or Yisrael. Those statuses are determined solely by the father’s lineage. It does not matter if the mother is a daughter of a Levi or Kohen; what matters is who the father is.
A child’s tribal status always follows his father: if his father is a Kohen or Levi, so too will he be, regardless of his mother’s background. In summary: bekhoir status depends on being his mother’s firstborn (petarechem), while priestly and Levitical status follows paternal descent.
4. Historical Shift: From Bekhoirim to Leviim
The Torah originally designated service in the Mishkan for the bekhoirim—the firstborn sons. Rashi notes that at first, Hashem chose them for this role. However, after they participated in worshipping the Golden Calf (Egil Hazahav), their privilege was revoked and transferred to the tribe of Levi.
The entire tribe of Levi (including both Kohanim and Leviim) replaced the original bekhoirim. The Torah details at length how this exchange took place numerically and logistically in Sefer Bamidbar—how each Levi was exchanged for a bekhoir, with special arrangements made for any surplus.
5. Future Restoration: Tzemach Tzedek vs Arizal on Mashiach’s Era
The Tzemach Tzedek teaches that when Mashiach comes, things will revert to their original state: service in the Beis Hamikdash will once again be performed by the bekhoirim, based on maternal descent (petarechem). This fits with deeper mystical ideas about feminine elevation in Messianic times—Eshes Chayil Ateres Bailo, where “the woman of valor becomes her husband’s crown.” In exile (galus) times, femininity (Nekeva) receives from masculinity (Zachar). But in future times (L’asid Lavo) this relationship will reverse: Malchus (the feminine sefirah) will become mashpia (influencer) even to Chochmah (the highest masculine sefirah).
This spiritual shift aligns with returning priestly service to those whose status as bekhoirim comes through their mothers.
6. Reconciling Tzemach Tzedek and Arizal: Who Will Serve?
The Arizal offers a different vision: when Mashiach comes, it will be specifically Leviim who become Kohanim—not necessarily all bekhoirim. This seems at odds with what Tzemach Tzedek says about restoring service to maternal-lineage firstborns.
An interesting possibility emerges from an earlier Rashi in our parsha: there were 300 more Levim than needed for exchange with Israelite firstborns because those Levim were themselves also bekhoirim. Perhaps these individuals—Leviim who are also maternal-lineage firstborns—will serve as Kohanim in Messianic times. This would satisfy both opinions: they would be both Levim (as per Arizal) and bekhoirim (as per Tzemach Tzedek).
7. Awaiting Clarification in Messianic Times
The Rebbe concludes that ultimately we do not know exactly how these roles will play out until Mashiach arrives. Whether priestly service returns to all bekhoirim or specifically those among Levim who are also bekhoirim remains to be seen. When Mashiach comes, we will discover how Hashem intends these laws to be fulfilled in practice.