The Gemara asks: מיתה מפלת או נישואין הראשונים מפילין.

Rav Soloveitchik points out that נישואין הראשונים מפילין is extremely difficult to understand.

How can the marriage itself be the cause of yibum?

Those very נישואין are what create the issur of אשת אח. Before she married his brother, she was permitted to the future yavam. The marriage is what makes her assur.

So how can the same marriage that creates the issur also be what creates the future נפילה to yibum?

Rav Soloveitchik explains that yibum must somehow already be built into the original אישות. The marriage does not only create איסור אשת אח; it also creates the framework that can later produce היתר יבום if the husband dies childless.

He sees this in the Rambam’s language regarding a woman who was divorced and then remarried:

הרי חזרה להיתרה

How can remarriage be called a “return to heter” when remarriage actually makes her אשת אח again?

The answer is that she has returned to an אישות that carries within it the potential for yibum.

That is the depth of the sugya: the very same נישואין that create the prohibition may also contain the future היתר.

Yevamos 108b: Get After Miun - Can she marry a Kohen?

Yevamos 108a: Why Kiddushin is considered a Miun - The Fascinating Chiddush of the Ohr Samayach

If mi’un uproots a marriage retroactively — תעקרינהו לנישואין קמאי — an obvious and powerful question emerges: if she is now treated as though she was never married, what was the status of all the relations she had with her husband? Shouldn’t every bi’ah retroactively become a ביאת זנות?

The answer brings us to a famous yesod of Rav Chaim Brisker: מיאון works מכאן ולהבא למפרע — “from now on, retroactively.”

Mi’un does not reveal that the marriage was fake or invalid from the beginning. Until the moment of mi’un, the marriage was completely real and halachically operative. She was his wife, he was her husband, and their relationship took place במסגרת נישואין. Only when she performs mi’un does Halachah uproot that marriage retroactively for the consequences that exist from this point forward.

That means the past has an extraordinary dual character. Looking at the moment when the bi’ah actually occurred, it was a completely legitimate ביאה של נישואין. But after mi’un, when determining her present and future halachic status, we can treat the original marriage as though it had been uprooted from its beginning.

This is the depth of מכאן ולהבא למפרע: the mi’un happening today can change how Halachah treats yesterday without saying that yesterday’s halachic reality never existed.

A classic piece of Brisker lomdus that answers a striking question on Yevamos 107b — and opens up a much bigger discussion about what “retroactive” really means in Halachah.

Yevamos 107a: החידוש של האבני נזר בעניין גדר ביאת זנות

Yevamos 106b: האם בחליצה צריך אמירת רוצה אני מצד האשה

What exactly must the yavam and yevamah have in mind when performing chalitzah?

The sugya on Yevamos 106a says that chalitzah requires the kavanah of both parties—but the Acharonim debate what kind of kavanah this actually is.

The Chacham Tzvi and Minchas Chinuch explore whether chalitzah requires the type of da’as needed to create a kinyan and a halachic chalos. The Beis Meir, Sho’el U’Meishiv, and Ketzos challenge that approach and raise the possibility that the requirement is one of kavanat hamitzvah and lishmah.

Rav Chaim Brisker and the Shaarei Yosher develop a fundamentally different understanding: the yavam and yevamah do not themselves create the heter. Rather, their kavanah gives the physical act its halachic identity as a ma’aseh chalitzah, and once that act exists, the Torah itself creates the resulting heter.

Along the way, we examine the Rambam, Ramban, Rashba, Tosafos, the cases of a katan and cheresh, the role of גדול עומד על גביו, and why removing a shoe can be either an ordinary physical act—or a halachic act powerful enough to release a yevamah to the shuk.

In Yevamos 105b, the dramatic encounter between Avdan and רבי ישמעאל ברבי יוסי becomes the basis for a powerful yesod in tochachah, lashon hara, and judging others. Why was Avdan punished only after he himself stepped through the talmidim—the very behavior for which he had just criticized רבי ישמעאל? The Chafetz Chaim connects this to the remarkable case of Yehu, who was commanded by Hashem to destroy the house of Achav, yet was later held accountable after he himself became connected to the same aveirah for which he had punished them. Together with the words of Rabbeinu Yonah, we explore a fundamental question: even when another person truly deserves criticism, can you be the one to expose or condemn him when you share the same failing? And even when speaking negatively is technically permitted for a genuine to’eles, how do we know that our motivation is really לשם שמים and not personal animosity or שמחה לאיד? A fascinating sugya about הפוסל במומו פוסל, the responsibility created when we judge another person, and the much higher standard the Torah demands from the one giving the תוכחה.

Yevamos 105a | Two Types of Teshuva

What makes the ten days between Rosh Hashanah and Yom Kippur so unique? The Rambam discusses Aseres Yemei Teshuva in two separate places — first describing a time when teshuva is accepted immediately, and later describing the shofar’s call to “wake up” and examine our lives.

Why does the Rambam separate these two ideas?

Based on an insight of Rav Soloveitchik, we explore two fundamentally different forms of teshuva: teshuva for a specific sin that we already recognize, and teshuva that begins before we even know what is wrong. Sometimes the challenge isn’t fixing an aveirah — it’s waking up, taking an honest look at the direction of our lives, and discovering what needs to change.

A powerful perspective on the avodah of Aseres Yemei Teshuva and the journey from Rosh Hashanah to Yom Kippur.

The Gemara teaches that even when the verbal recitation of Chalitzah is not essential, the Yavam and Yevamah still have to be capable of saying it. But what happens when someone can speak perfectly well — and simply cannot hear?

A fascinating discussion in the Rashash and Ramban may reveal two very different reasons why this is a problem. Is the issue that the person is not considered capable of performing the Kriah, or is there a separate requirement for Beis Din to teach them what to say?

An interesting case — where Beis Din teaches the person first and only afterward they lose their hearing — brings the distinction into sharp focus.