Yibum, the biblical institution of levirate marriage, seems awkward and antiquated. It occurs when a man dies without children, and leaves behind a widow. It is a mitzvah for the brother of the deceased to perform yibum, and move in with the widowed sister-in-law and take her as his wife. (When the widow and her brother-in-law choose not to perform yibum, a ceremony called “chalitzah” takes place.)  Yibum is the polar opposite of romantic love, and is the ultimate arranged marriage.

Already in the times of the Talmud, there was discomfort with yibum. Marrying a widowed sister-in-law is ordinarily prohibited, and only allowed in a case when the deceased brother left no children; the former prohibition is now turned into a mitzvah. Abba Shaul, who lived in the second century, felt that yibum should be forbidden for everyone, because this previously prohibited relationship is set aside when one is performing yibum for the sake of the commandment; and it is impossible to be certain that the brother has only pure intentions.

The other rabbis disagreed with Abba Shaul, and encouraged yibum. This debate continued on through the centuries; in the 7th and 8th centuries, the Babylonian Yeshiva of Sura encouraged yibum, while the nearby yeshiva in Pumpedita discouraged it. Similarly, in the Middle Ages, Sephardic halakhists encouraged yibum, while Ashkenazic authorities discouraged or forbade it. As a consequence, yibum has not been practiced in Ashkenazic communities for hundreds of years. In 1950, the Sephardic and Ashkenazic Chief Rabbis of Israel, Rabbi Ben Zion Uziel and Rabbi Isaac Herzog, attempted to institute a universal policy against yibum in the State of Israel. A year later, a Yeminite couple presented themselves to the Rabbinical Court in Petach Tikvah, asking for the right to perform yibum. The man was shocked that his arrival in the State of Israel would prevent him from performing this mitzvah. Rabbi Ovadiah Yoseph, who was then a 30-year-old newcomer to Israel, wrote a lengthy responsa defending the historic Sephardic practice, and disagreeing with the Chief Rabbinate’s new policy. Ultimately, Rav Ovadiah’s view proved decisive; and in a well-publicized case in 1985, Rabbi Mordechai Eliyahu gave permission to a widow and her brother-in-law in Ashkelon to perform yibum, and marry.

While yibum is uncommon, it plays a significant role in biblical thought. A close reading of the Tanakh leads to the realization that the theme of yibum is a foundation of nationhood. It plays a central role in two biblical narratives: Tamar and Judah in the book of Genesis, and Ruth and Boaz in the Book of Ruth. In both cases, a somewhat reluctant man is called upon to marry the widow of a deceased relative and build a family, after others refuse to do so. And both of these yibum marriages are performed by prominent ancestors of King David, the founder of Israel’s dynastic monarchy. Clearly, yibum is central to the future Jewish commonwealth. But why?

The answer lies in understanding what yibum represents. The Torah explains that when a baby is born to the new marriage, it will “carry on the name of the dead brother, so that his name will not be blotted out from Israel” (Deuteronomy 25:6). The brother who has passed away will never be forgotten; the new baby will carry on his name and legacy. (There is a dispute over whether the verse is metaphorical, or actually means that the child should be given the identical name as the deceased brother; either way, the baby represents a way of keeping the memory of the deceased brother alive.) Yibum is a difficult sacrifice for the brother who marries the widow; his new son is not quite his own, as he has dedicated this child to the legacy of his dead brother. In performing yibum, the living brother accepts responsibility to carry on his brother’s legacy and care for the widow. In the ancient world, yibum is a powerful act of solidarity, where one brother sets aside his own interests to stand in for the other.

Solidarity is critical to building a nation. The Tanakh sees the Jewish nation as a family writ large; and the lessons of yibum are also lessons of leadership. Every nation will have multiple tribes; but it can only succeed if those tribes stand up for each other, as if they were brothers, and ensure each other’s existence. When King David ascends to the throne, his first responsibility is to find a way to unite all the tribes; and that remains the first responsibility of every future king and leader.

Yibum teaches the importance of unity and solidarity, both in families and in nations. This message is popular, and oft repeated, both in synagogue pulpits and at dinner tables. The problem is that in real life, this lesson is often ignored.

Yibum teaches the importance of unity and solidarity, both in families and in nations . . . The problem is that in real life, this lesson is often ignored.

One of the more fascinating aspects of the biblical passage regarding yibum is the phrase “when brothers dwell together” (Deuteronomy 25:5). In Hebrew, the two root words for dwell (yeshvu) and together (yachdav) are only grouped together in three other passages in the Tanakh. They are found in Psalm 133, where it declares “Behold, how good and how pleasant it is for brothers to dwell together in unity!”  This Psalm is about the crowds gathering in the Temple, with a multitude of different tribes joining together, and represents the ideal realization of the values found in yibum. But the two other Biblical parallels remind us how difficult unity actually is; both are in cases when a family is splitting apart.

When Abraham and his nephew Lot separate from each other, they do so because “their possessions were so great that they could not dwell together”; a battle between their shepherds ensues. When Jacob and Esau take each other’s leave, it is because “their possessions were too many for them to dwell together.” In both cases, a family dissolves because of ambition. They have too many possessions, and because of the conflicts that arise, they cannot dwell together anymore. Unity makes for fine sermons; but all too often, it is much easier for brothers to dwell apart.

When I was in yeshiva, I had a teacher who would hammer away at the unconscious hypocrisy about unity we all carry. He would repeat the words of a student who once told him: “of course I love Jews. I love the Jews in the Soviet Union, I love the Jews in Syria. It’s my roommate I can’t stand!” We all talk a good game about unity, but don’t realize that this rhetoric masks how difficult it is to achieve. We can’t ever take for granted that two brothers will dwell together. This is true of families and communities; and at a time when the various Jewish tribes seem to be drifting further apart, this is certainly true of the Jewish people as a whole.

Rabbi Chaim Steinmetz is the Senior Rabbi of Congregation Kehilath Jeshurun in New York.