The Covenant That Draws the Map

The Hook

The second chapter of the laws of forbidden relations is, for most of its length, a list of the women a man may never marry. His father’s wife. His son’s wife. His sisters, his aunts, his wife’s mother and daughters. It reads like a map of a family with certain roads permanently closed.

And then, in the very last lines, the Rambam does something unexpected. He turns from what is forbidden to what is encouraged. A man may marry the widow of his brother’s son. He may marry a woman and her niece. And then: it is a mitzvah from the Sages for a man to marry his sister’s daughter, as the prophet Isaiah says, “Do not turn away from your own flesh.”

Tucked between those two poles is a sentence that explains the whole chapter. When a man has a relationship with a woman outside of marriage, the Rambam says, her relatives do not become forbidden to him by Torah law. “One is considered an ervah because of the other only in the instance of marriage, not in an instance of promiscuity.” Only marriage draws the lines. So what exactly is the power of marriage, that it can reshape a family map forever? And why does a chapter of closed roads end with an open door?

Lines That Last Forever

The chapter begins with four women: the wife of a man’s father, the wife of his son, the wife of his brother, and the wife of his father’s brother. Each is forbidden to him forever, whether she was only betrothed or fully married, whether her husband is living or has died, whether she was divorced. The single exception is the widow of a brother who died without children, whom the Torah itself calls on a brother to marry so that the departed brother’s name will continue.

Notice that these four are not blood relatives. They became part of a man’s family through someone else’s marriage, and yet the line around them is permanent. Divorce does not erase it. Death does not erase it. Once a woman has entered the family through marriage to a father, a son or a brother, she stands in that place for good.

Then the Rambam turns to blood. A man’s sister, whether from his father or his mother, is forbidden to him, and it makes no difference whether she was born within a marriage or outside of one, for the Torah says “born at home or born beyond.” The same is true of his mother’s sister and his father’s sister. And a daughter born to a man outside of marriage is forbidden to him by the Torah itself; the Rambam explains that the Torah did not need to state it, since it already forbade a daughter’s daughter. Blood ties do not depend on how a person came into the world. They simply are.

Here the Rambam adds a careful distinction. The Torah speaks of “the daughter of your father’s wife, your father’s offspring.” So when a man’s father marries a woman who has a daughter from a previous husband, that daughter is not his father’s child, and she is permitted to him. The commentaries add that this is so even if the two grew up in the same home like brother and sister. The halacha is not governed by appearances. It follows the real lines of the family.

What Marriage Creates

The middle of the chapter turns to the relationships that marriage itself brings into being. When a man betroths a woman, six of her relatives become forbidden to him forever: her mother, her two grandmothers, her daughter, and her two granddaughters. This holds whether the betrothal leads to marriage or ends in divorce, during her lifetime and after her death. During her lifetime, the Torah treats a transgression with one of them with the utmost severity; after her death it remains forbidden under kareit, though the court no longer executes. Her sister, a seventh relative, is forbidden to him only while his wife lives.

The Rambam then teaches something about fairness. If a man transgresses with one of these relatives, his own wife does not become forbidden to him, because she did nothing wrong. The sin is his. It does not reach backward to harm the innocent partner in the marriage.

And then comes the sentence quoted above. A relationship outside of marriage does not create these lines at all by Torah law. If a man had such a relationship with a woman and her daughter, the Torah sees two unrelated women. If a man’s father or son overpowered or seduced a woman, she is not considered “the wife of” his father or son, and she is permitted to him. The verses speak of “taking”, of marriage, and where there is no marriage there is no new family.

Why should marriage have this power? The Talmud, at the very beginning of Tractate Kiddushin, explains the word itself: a man who betroths a woman makes her forbidden to the whole world like something consecrated to the Temple. Kiddushin is a word of holiness. It does not merely join two people; it sanctifies a bond, and a sanctified bond reorders everything around it. The mother of one’s wife becomes a mother-in-law, a fixed place in a sacred structure. A relationship without that sanctity, however intense, has no power to build anything. It can only break.

Fences and an Open Door

The Sages, knowing human nature, added fences. A man who had an improper relationship with a woman may not marry one of her close relatives while she is alive, because she would visit, they would be familiar with each other, and one transgression would lead to another. Even if he was only suspected of such a relationship, he should not marry her relative during her lifetime, though if he already did, he need not divorce. And a man rumored to be involved with a woman forbidden to him should not live on the same lane or be seen in her neighborhood. The Rambam records an incident in which the Sages had a man disciplined simply for passing the entrance of a mother-in-law with whom he had been rumored.

That can seem strict until we hear the Talmud’s observation, which the Alter Rebbe develops in the nineteenth chapter of Tanya: a person does not sin unless a spirit of folly enters him. In the moment of transgression, the Alter Rebbe explains, a person forgets that the act separates him from G-d; a kind of foolishness clouds what the soul knows. The fences of the Sages are an answer to that spirit of folly. They keep a person away from the situations in which the mind is most likely to be clouded. A wise person does not test himself at the edge. He stays far enough back that the edge never comes into view.

And then, after all the closed roads, the door opens. A man whose father or son married a woman may himself marry her mother or daughter. He may marry the widow of his brother’s son. He may marry a woman and her niece together. And the Sages call it a mitzvah to marry his sister’s daughter, and some say his brother’s daughter too, because, as the commentaries explain, the natural affection between close relatives gives a marriage fertile ground to flourish. “Do not turn away from your own flesh.”

The Alter Rebbe, in the thirty-second chapter of Tanya, teaches that all Jews are true brothers, because their souls come from one source, the one Father above; only their bodies are separate. Closeness is not a danger to be avoided. It is the deepest truth about us. The laws of forbidden relations do not ask us to be distant from family. They ask us to give each relationship its proper form, so that the love inside a family can be safe, clear and lasting.

The Unifying Principle

The family, in this chapter, is a map drawn by two hands. One hand is birth: sisters, aunts, daughters, bound by blood regardless of the circumstances of their birth. The other hand is covenant: the kiddushin that creates in-laws and step-relations and fixes them in place, sometimes forever. Both hands draw permanent lines. What does not draw lines is a relationship outside of covenant. It creates nothing, because it was not built on holiness.

The principle, then, is that holiness is creative. A consecrated marriage is so real that it reshapes the whole family around it, and the Torah treats those new relationships with the same seriousness as the ones given by birth. The boundaries are not arbitrary prohibitions laid over a family from outside. They are the visible outline of what marriage actually makes. And inside those boundaries, the Torah not only permits closeness. It commands it.

Modern Application

Many families today are blended, with parents who remarried, step-siblings, and in-laws from more than one marriage. This chapter is a reminder that the Torah has always known such families, and that it maps them precisely rather than by impression. Who is forbidden and who is permitted follows the real lines of blood and marriage, not how close people feel or how they were raised. For any practical question, of course, a family should ask a competent rav, but the underlying idea is worth holding: every relationship in a family has a true shape, and holiness lies in honoring it.

The chapter also speaks to the respect that in-law relationships deserve. A mother-in-law, a son’s wife, a brother’s wife: the Torah treats these as fixed and sacred places. Warmth toward them is good and right, and it is lived with a natural dignity and modesty that keeps every relationship clear. That dignity is not coldness. It is what allows a family to be close for decades without confusion.

And the Sages’ fences teach a practical humility. Most of us do not fall because we decide to. We drift into situations where a spirit of folly can enter. Guarding our circumstances, choosing not to linger where we should not be, is not a lack of trust in ourselves. It is wisdom about how people actually work.

There is a well-known teaching of the Baal Shem Tov that everything a person sees or hears is meant as a lesson for his own service of G-d. When we read of the man whom the Sages disciplined for walking past a door, the point is not to judge him from a distance. The point is to ask where, in our own lives, we keep walking past doors we already know we should avoid. The Rambam recorded that incident so that each reader would quietly take its lesson home.

Finally, the closing mitzvah asks something of us too. “Do not turn away from your own flesh.” Within the lines the Torah draws, family is meant to be close. The laws of holiness are not an invitation to distance. They are the frame that makes closeness possible.

The Closing

This chapter begins with women forbidden forever and ends with a mitzvah to marry within the family. In between it teaches that only marriage draws the map, because only marriage is holy enough to create. The lines it draws are permanent, the fences around them are wise, and the space inside them is meant to be filled with love.

Honor the lines that birth and covenant have drawn, keep a wise distance from the edges, and then do not turn away from your own flesh. That is how a family becomes holy.