Li-zchus my beloved friends 

Moshe Yehuda ben Pesha Dina - Jonathan Hanus 

Rebbe Shmuel Stein

Rebbe Chaim Schreck 

Rebbe Eytan Feldman 

And their entire families for much bracha and hatzlacha in EVERYTHING!!

What is the relationship between זיקה [not the disease but the linkage between a woman and her late husband's brother until she either marries him with yibum or performs chalitza] and יבום? 

Is it that because there is יבום there is also זיקה? Or the opposite - because there is זיקה there is also יבום? Where does it start? [This is similar to the chakirah of Rabbeinu regarding kiddushin - Is the woman מקודשת because she is נקנית or is she נקנית because she is מקודשת?]

Let us look at a gemara in Yevamos [5b-6a]:

אשכחן דאתי עשה ודחי לא תעשה גרידא לא תעשה שיש בו כרת היכא אשכחן דדחי דאיצטריך עליה למיסרה

We have found that a positive mitzva overrides a regular prohibition. However, where do we find that a positive mitzva overrides a prohibition that includes karet, as the phrase “with her” is necessary to prohibit her? It was mentioned previously that the superfluous phrase “with her” teaches that the mitzva of levirate marriage does not override the prohibition against taking a wife’s sister. However, why is this necessary? Why would it have been assumed that a positive mitzva is so powerful that it overrides even a prohibition that is punishable by karet?

איצטריך סד"א תיתי מכבוד אב ואם

The Gemara suggests: The inference from “with her” is necessary, as were it not for this inference it might be assumed that the mitzva of levirate marriage overrides the prohibition against marrying one’s wife’s sister despite the fact that this prohibition incurs karet, since it could enter your mind to say that this halakha is derived from the mitzva of honoring one’s father and mother.

דתניא יכול יהא כבוד אב ואם דוחה שבת ת"ל (ויקרא יט, ג) איש אמו ואביו תיראו ואת שבתותי תשמורו כולכם חייבין בכבודי

As it is taught in a baraita: One might have thought that honoring one’s father and mother overrides Shabbat; therefore, the verse states: “You shall fear every man his mother and his father and you shall keep My Shabbatot,I am the Lord your God” (Leviticus 19:3). The baraita explains the derivation from the verse: All of you, both parent and child, are obligated in My honor,and therefore honoring one’s parents does not override the honor of God, Who commanded the Jewish people to observe Shabbat.

מאי לאו דאמר ליה שחוט לי בשל לי וטעמא דכתב רחמנא את שבתותי תשמורו הא לאו הכי דחי לא

The Gemara analyzes this baraita: What, is it not referring to a situation where his father said to him: Slaughter for me, cook for me, or any other labor prohibited on Shabbat on pain of karet? And the reason that the Merciful One specifically writes: “Keep My Shabbatot,” is to warn against violating the prohibition against performing labor on Shabbat, a transgression which incurs karet, for the purpose of honoring one’s parents. It may therefore be inferred that if that was not so, the positive mitzva would overrideShabbat. It is therefore possible to deduce from here that in general, positive mitzvot override even prohibitions that entail karet. The Gemara rejects this proof: No,

לאו דמחמר ואפי' הכי לא דחי

the reference is not to a situation where a father demanded that his child perform prohibited labor on Shabbat that entails karet. Rather, he instructed him to transgress the prohibition against driving a laden animal. Although it is prohibited to cause animals to work on Shabbat, this does not entail the penalty of karet, as it has the status of a regular prohibition. And this shows that if one’s father told him to desecrate Shabbat by driving a donkey, even so, the positive mitzva to honor one’s parents does not override the prohibition against driving a laden animal. 

אלא דקיימא לן דאתי עשה ודחי לא תעשה ליגמר מהכא דלא לידחי

The Gemara asks: If so, rather than that principle in which we maintain that a positive mitzva comes and overrides a prohibition, let us derive from here that it does not override even a regular prohibition. Just as it was inferred above from the case of ritual fringes, in which the positive mitzva overrides the prohibition against diverse kinds, that all other positive mitzvot similarly override any prohibition, perhaps one should infer from the case of honoring one’s parents that positive mitzvot do not override prohibitions at all.

וכ"ת שאני לאוי דשבת דחמירי והא תנא בעלמא קאי ולא קפריך

And if you say that one should not infer this from here, as the prohibitions of Shabbat are different in that they are more serious, and for this reason the mitzva to honor one’s parents does not override these prohibitions, this cannot be the case, as the tanna speaks generally of a father who instructs a son to perform a regular prohibition, not to desecrate Shabbat, and he does not raise any difficulty of this kind.

דתניא יכול אמר לו אביו היטמא או שאמר לו אל תחזיר יכול ישמע לו ת"ל (ויקרא יט, ג) איש אמו ואביו תיראו ואת שבתותי תשמורו כולכם חייבין בכבודי

As it is taught in a different baraita: One might have thought that if one’s father said to his son, who is a priest or nazirite: Be rendered ritually impure with impurity imparted by a corpse, so as to bring me an item from a ritually impure place, or if he said to him: Do not return this lost item, it might have been supposed that his son should obey him. Therefore, the verse states: “You shall fear every man his mother and his father and you shall keep My Shabbatot, I am the Lord your God” (Leviticus 19:3). This verse teaches: All of you are obligated in My honor. This proves that the tanna does not differentiate between desecrating Shabbat, which is a severe prohibition, and a priest becoming ritually impure with impurity imparted by a corpse, which is a lighter prohibition.

אלא משום דאיכא למיפרך

Rather, the Gemara rejects this line of reasoning and accepts the claim that the baraita does not speak of one whose father asked him to desecrate Shabbat by performing a prohibited labor that entails karet, but of a father who instructed his son to drive a laden animal. As for the difficulty that this apparently indicates that a positive mitzva does not override any type of prohibition, the reason that this is not the case is because there is room to refute this argument.

מה להנך שכן הכשר מצוה

Says Rashi: 

אלא - לעולם דאמר ליה שחוט לי בשל לי ואפ"ה לא איצטריך עליה דאיכא למיפרך מה להנך שחוט לי בשל לי שכן הכשר מצוה בחילול שבת בעקירת לא תעשה הוא מקיים עשה דכיבוד וזהו הכשר קיומו ואי אפשר לקיימו בלא עקירת לאו הלכך אי לא כתב את שבתותי תשמורו ה"א לידחי אבל ייבום לא זה בלבד הכשר קיום העשה שהרי יכול לחלוץ ולא יעקור לאו של ערוה ולא איצטריך עליה:

Rashi explains that we need a pasuk forbidding one from being מחלל שבת to serve his father because in such an instance this is the ONLY WAY [that is the meaning of הכשר מצוה in this context according to the much disputed understanding of Rashi] to fulfill the mitzva. This is in contradistinction to יבום which is NOT the only way to fulfill the mitzva because there is also the חליצה option before the woman. Therefore, no pasuk is needed to tell us that יבום does not override the איסור of אחות אשה. 

Now, if יבום was the mitzva [and the זיקה a result of the מצות יבום] then we would probably say that the mitzva can override the לא תעשה [if not for the pasuk precluding that possibility]. It would be similar to כיבוד אב insofar as the fact that the only to fulfill the mitzva of יבום is by performing יבום. 

But Rashi learns that the process begins with זיקה and the יבום is an outgrowth. Thus, there is no logical reason to assume that יבום would override the לא תעשה because זיקה offers us two distinct possibilities - יבום or חליצה. So why not take the חליצה option and avoid overriding the aveira??!!  

In the words of Rabbeinu [צפנת פענח שם]:

"דכיון דחזינן דע"י החליצה שמפקיע הזיקה בטלה היבום, חזינן דהעילה היא הזיקה ולא שייך עשה דוחה ל"ת".

In Tzafnas Paaneach Hilchos Nedarim [Page 30] he explains more:

דגבי כבוד אב ובנין בית המקדש הוה המצוה הדבר, ובלא הדבר ליכא מצוה. אבל גבי יבום, כיון דחזינן דאם חלץ לה פקעה המצוה, א"כ נמצא דאין המצוה זה הדבר רק ע"י הזיקה נתחייב בהמצוה וא"כ י"ל דהערוה עושה פעולה שתפקע הזיקה וממילא ליכא מצות יבום. 

Regarding Kibbud Av and the building of the Beis Hamikdash - those are the mitzvos and there are none other. But with regard to יבום, since we see that he is released from the obligation of mitzva by performing חליצה, it must be that the mitzva starts with זיקה.  

With this understanding we can answer the question of Tosfos [Yevamos 9a ד"ה והרי אסור]: 

בכל דוכתי פשיטא ליה להש"ס דחייבי לאוין לר"ע דאמר אין קידושין תופסין בחייבי לאוין לאו בני חליצה וייבום נינהו כמו חייבי כריתות

Everywhere, it is clear to the Gemara that R. Akiva, who says that Kidushin does not take effect on Chayavei Lavin, holds that Chayavei Lavin do not do Chalitzah or Yibum, just like Chayavei Kerisos.

ותימה לר"י דאמאי לא אמרינן נמי לר"ע דליתי עשה ולידחי לא תעשה.

Asked the ר"י: Why don't we say also according to R. Akiva that Aseh Docheh Lo Sa'aseh [to permit Yibum of Chayavei Lavin]? 

(Tosfos ha'Rosh - perhaps he learns from a Hekesh equating Anusas Aviv, which is Chayavei Lavin, to Eshes Aviv, who is exempt from Yibum and Chalitzah.)

But according to what we have been saying the answer is simple: 

."כיון דסבר ליה דאין קידושין תופסין עי"ז פקעה הזיקה דלא עדיפא מקדושין"

Since R' Akiva holds that Kiddushin with חייבי לאוין does not take effect, there is also no יבום. Since the mitzva starts with זיקה [as we proved], in the case of חייבי לאוין the mitzva never gets off the ground. There is only a mitzva of יבום if there is a זיקה but there is no זיקה just as there is no קידושין because זיקה is no stronger than קידושין!!

[עפ"י משנת רבינו יוסף הרוגוצ'אבי]