Most of Tractate Bekhorot deals with animals—specifically, the obligation to give the firstborn offspring of every kosher animal (and also donkeys) to a priest. But it is not only firstborn animals that belong by right to the priesthood: The same is true of the firstborn son of every Jewish mother. As it says in Exodus 13, “Sanctify to Me all the firstborn, whatever opens the womb among the children of Israel, both of man and of animal, it is Mine.” However, not all Jewish mothers are like the biblical Hannah, who willingly handed over her son Samuel to the high priest, Eli. The Torah recognizes that most mothers want to keep their sons, which is why they are allowed to “redeem” or buy back the child by paying a priest five silver coins, due once the child is 30 days old.
Chapter 8 of Tractate Bekhorot focuses on this obligation to redeem the firstborn son with money. In particular, the rabbis are interested in the way it interacts with another law pertaining to firstborn sons, stated in Deuteronomy, which entitles the firstborn son to a double share in his father’s estate—“for he is the first of his strength, the right of the firstborn is his.” In other words, the Torah establishes two categories of firstborn sons, each with different rights and obligations. The firstborn son of a mother, who “opens her womb,” must be bought back from the priests, while the firstborn son of a father, who is “the first of his strength,” receives a double inheritance.
In many cases, the same child will be the firstborn of each parent. But this is not always true, as the mishna in Bekhorot 46a explains: “there is a son who is a firstborn with regard to inheritance but is not a firstborn with regard to redemption from a priest,” and vice versa. The most obvious way this could happen is if either the father or the mother has been married before: If a man who is childless marries a widow who has a child and they have a son together, it will be the father’s firstborn but not the mother’s.
But the rabbis are concerned with more ambiguous cases. Some of these arise from the particular definition of birth used by the Torah: “opening the womb.” Say a woman becomes pregnant for the first time and has a stillbirth or miscarriage, and then becomes pregnant again and gives birth to a boy. Technically, it was the first pregnancy that opened her womb, even though only the second produced a living child. As a result, the mishna says, the son does not have to be redeemed from the priests.
But does every miscarriage open the mother’s womb? The answer depends on how advanced the pregnancy is and the state of development of the fetus—which the rabbis measure not according to weeks of pregnancy but according to how closely the fetus resembles a human being. According to Rabbi Meir, if a fetus resembles “a type of domesticated animal, undomesticated animal, or bird,” it is sufficiently developed to count as opening the mother’s womb. If, on the other hand, a woman miscarries and delivers a sac full of water or blood, or “a mass resembling a fish, or grasshoppers, or repugnant creatures, or creeping animals”—in other words, something that does not appear to be an animal at all—then it does not open the mother’s womb, and a boy born subsequently has to be redeemed from the priests as a firstborn.
A live birth isn’t required to open a woman’s womb; conversely, not every mother of a living child has her womb opened. That is because, as we learn in Bekhorot 47b, a baby born by cesarean section does not legally open its mother’s womb. This makes a certain kind of sense, but it can have paradoxical results. Say a woman has a son who is born by cesarean section, and then another son who is delivered vaginally. The first son is not his mother’s firstborn, because he was not “born” in the legal sense; for the same reason, he doesn’t count as his father’s firstborn. The second son, however, also can’t be his father’s firstborn, because he is not “the first of his strength” since he has an older brother. One might think that the second son would at least be the mother’s firstborn, then, and that is indeed the opinion of Rabbi Shimon; but the rabbis say he is not, because he is not actually her first child. Oddly, then, a couple can have two sons but no firstborn.
As the notes to the Koren Talmud explain, however, it is not clear whether this discussion is meant to reflect real-life experience. That is because it is uncertain whether, in the ancient world, there was ever a case of a woman surviving a cesarean section and living to give birth again. In a world without modern surgical techniques, hygiene, antibiotics or anesthesia, the operation was performed only to remove a living fetus from a mother who had died or was about to die in childbirth. (Maimonides, for one, didn’t think a cesarean section was survivable, and considered this whole discussion as one of the Talmud’s many hypothetical debates.) This is one of several places in the Talmud where modern technology has made real a question that was once purely theoretical, since in the United States today, a third of babies are delivered via cesarean.
The Talmud goes on to consider other situations that are almost equally unlikely. Imagine that a man had two wives—polygamy, of course, was legal in Talmudic times—and they each gave birth to a firstborn son at the same time, and the babies were mixed up so it wasn’t certain which one came from which mother. The man would owe the priests 10 sela, five for each baby, and he would be within his rights to give five to one priest and five to another. Now imagine that he paid the fee early, before it came due on the 30th day of the babies’ lives, and then before the 30th day, one of the babies died. Would he be able to reclaim five sela as a refund, since the payment was no longer required for a baby who died before its 30th day? The problem, the mishna explains in Bekhorot 48b, is that each priest could refuse to pay back the money, claiming that his five sela was intended for the living child, and the other priest’s five sela was for the child who had died.
There’s undoubtedly something a little distasteful about this kind of theorizing, because it seems to reduce the death of a child to a purely financial problem. But of course, this whole discussion is not a reflection of what actual bereaved parents would feel or do in real life. The Talmud is presenting a logical conundrum, which has to be solved because the law requires conceptual clarity—even if it is never put into practice.