The same day came to him the Sadducees, which say that there is no resurrection, and asked him, saying, “Master, Moses said, If a man die, having no children, his brother shall marry his wife, and raise up seed unto his brother. Now there were with us seven brethren: and the first, when he had married a wife, deceased, and, having no issue, left his wife unto his brother: Likewise the second also, and the third, unto the seventh. And last of all the woman died also. Therefore in the resurrection whose wife shall she be of the seven? for they all had her.” - Matthew 22: 23-28, KJV
In this episode from the gospel according to Matthew, Jesus’ interlocutors describe a compound case of levirate marriage in an attempt to stump the Rabbi. The Sadducees ascribe the social practice to Moses, the recorder of the Torah. The practice of levirate marriage (a.k.a. yibbum in Judaism) is set forth as law in Deuteronomy 25: 5ff,
“5 If brethren dwell together, and one of them die, and have no child, the wife of the dead shall not be married abroad unto one not of his kin; her husband's brother shall go in unto her, and take her to him to wife, and perform the duty of a husband's brother unto her. 6 And it shall be, that the first-born that she beareth shall succeed in the name of his brother that is dead, that his name be not blotted out of Israel.”
The sociological reasons typically cited for this practice argue that the purpose here is to ensure that the widow has offspring to take care of her in her old age. But the reason cited in the text itself is explicitly to keep alive the “name” of the brother who has died. That is, to preserve his family line. It is this explanation that I would like to dwell on further insofar as it points to an even deeper and more foundational reason for the practice of levirate marriage. Levirate marriage is a deterrent to fratricide, at least in the milieu of ancient Israel.
To establish this explanation, we need to recall the story of Judah’s son, Onan in Genesis 38. Onan had an older brother named Er. Er was Judah’s first-born son. Onan was the second-born, and Shelah was third. The eldest of Judah’s 3 sons gets himself killed by God because of some wickedness that is not explained to us. So it is up to his younger brother, Onan, to have sexual relations with Er’s widow, Tamar. Thereby Onan fulfills his duty as a levirate and provides her a child that would be considered the offspring of Er, not its biological father, Onan.
But Onan, we are told, interrupts the sex and “spills his seed” on the ground. He does not want to fulfill his obligation to his dead brother. As a consequence, God kills Onan, too. Judah is now down to one remaining son, and the subsequent narrative describes how it will be Judah himself who gets Tamar pregnant and secures the family line, making her an ancestor of King David and Jesus (Matt 1:3).
But let us back up just a bit here and consider why it is that Onan does not want Tamar to have offspring in Er’s name. We are not told, and I can find zero, zip, zilch speculation in the literature as to Onan’s possible objection over “giving seed to his brother”, other than some assumed grudge that perhaps Onan had with his older brother. But when we consider the inheritance customs in ancient Israel, the reason becomes clear - for at the root of all evil one finds money.
First, we need to dispense with the typical explanation for the purpose of levirate marriage, namely that the widow will have offspring to take care of her. There are other solutions to this problem. The most straightforward being that the widow enjoins herself to the family/clan of her dead husband (without child-bearing), or she returns to her family/clan of origin. Being joined to a surviving brother in levirate marriage would seem to be an extreme solution if the problem needing to be solved is merely the well-being of the widow.
Since Er was the first-born son of Judah, by Torah law and Israelite custom he was going to inherit a double-portion of Judah’s property upon Judah’s death (Deut. 21:15-17). If Judah had only three sons, it means that Er was going to inherit 50% of his father’s estate, double what each of his brothers would inherit. Onan and Shelah would each get 25%. With Er’s untimely demise, Onan could expect a windfall. Instead of 25% of Judah’s estate, Onan now stands to inherit 66.6% of the total, since he is now the eldest son!
But if Onan is obliged to impregnate Tamar and raise-up for her a son who will preserve the family line of Er, this windfall evaporates. Tamar and her offspring by Onan would inherit the original 50% that was to come to the dead first-born, Er. So now we see a perfectly rational, selfish reason for Onan to spill his seed on the ground. He goes into Tamar to keep up appearances, but makes every attempt to spoil the outcome intended by the levirate marriage custom. Why? Because the offspring of Tamar is going to cost him a large chunk of inheritance. In later forms of Judaism (Talmudic and Rabbinic) there may be provision for the levir/yibbum brother to get an increased share of the inheritance, or even the double-share. There is no indication that this was the case in Ancient Israel.
Additionally, this perspective on the account makes God’s anger more understandable. I neither need to agree nor disagree with those who cite the events in Genesis 38 as evidence for the immorality of birth control. I am setting that topic to the side; birth control does not concern me here. Rather, I have identified at least one other understandable reason for God’s wrath in this situation: Onan is threatening the foundational social norm of levirate marriage. This norm (pre-Mosaic “law” if you will) deters one brother from killing another (especially the first-born), since the financial motivation is eliminated. If I am expected to replace my brother’s life with that of another offspring from my own seed, what’s the point?
But perhaps one thinks he can game the system like our guy Onan has tried to do in Genesis 38. Indeed, this might explain why this episode was included in the book in the first place. If some Israelite is thinking to thwart the levirate arrangement by coitus interruptus, God may strike him down summarily.
Fratricide is a key problem in the book of Genesis. It is the first, shocking, violent act recorded after Adam and Eve are evicted from the garden of Eden. Cain has a resentment against his brother Abel and kills him. In this case of fratricide, Cain happens to be the first-born and the resentment is not related to money, but rather Cain’s resentful over the favor of God for Abel’s sacrifice.
Early human societies needed ways to deter siblings from killing each other. To this day, inheritance disputes tear families apart. According to a Wall Street Journal report, around 70% of heirs lose part of their inheritance because of disputes. Today we have well-established laws regarding murder and manslaughter, but in early human societies there were no codified laws. Two brothers tending their father’s flocks far away from family, town or village and among steep cliffs and deep ravines makes for a setting where one brother can easily have an “accident”. The form of levirate marriage practiced in 2nd millenium timeframe of the Patriarchs was one tool among whose deep purposes was perhaps to dissuade such accidents from taking place.