Yevamot 2 - 8
Yibum: “Brotherly Love”
“From here we learn that a positive command (an ‘aseh’) pushes off a negative command (a ‘lo ta’aseh’).”
It is evident from the name of this masechta that the theme of our current tractate is the mitzvah of yibum — what is known is English as “the Levirate Marriage.” This mitzvah and its rules are the predominant topics throughout the mesechta. Despite this English term, “Levirate,” it should be clarified that this mitzvah has nothing to do with Levites in particular. Rather, it stems from the Latin word for brother-in-law — levir — and is a fitting description of the nature of this mitzvah.
The Torah states:
If brothers reside together, and one of them dies having no offspring, the dead man's wife shall not marry an outsider. Rather, her husband's brother shall be intimate with her, making her his wife, thereby performing the obligation of a husband's brother (yibum). And the eldest brother who performs the levirate marriage… will succeed in the name of his deceased brother, so that his deceased brother's name will not be obliterated from Israel. But if the man does not wish to take his brother’s wife, she will go up to the gate, to the elders, and say, “My husband’s brother has refused to perpetuate his brother’s name in Israel; he does not wish to perform the obligation of a husband’s brother with me.” Then the elders of his city will call him and speak with him, and he will stand up and say, “I do not wish to take her.” Then his brother’s wife will approach her brother-in-law in the presence of the elders and remove his shoe from his foot. And she shall spit before his face and answer him, saying, “Thus will be done to the man who will not build up his brother’s household!” And that family will be called in Israel, “The family of the one whose shoe was removed.” (Devarim 25:5-9)
A novel concept can be seen in the Torah permitting a brother-in-law to marry his deceased brother’s wife. Under any other circumstance, a man’s wife would be absolutely forbidden to his brother. This forbidden relationship would be one that would violate a severe Torah prohibition. However, for the sake of yibum, the brother is not only permitted to marry his brother’s widow, but doing so is considered a mitzvah. (It should be emphasized that nowadays, due to a lack of the necessary purity and spirituality that existed in earlier generations, yibum is no longer an option and chalitza is always done instead.)
In the course of the gemara’s discussion of this phenomenon of the Torah permitting an act which is normally forbidden, there is extensive focus on the principle of a positive command (an ‘aseh’) pushing off a negative command. The gemara states that a source for this mitzvah is the Torah permitting shatnez for the mitzvah of tzitzit. There is a juxtaposition of verses in the Torah, indicating that although the Torah normally forbids shatnez, the mitzvah of tzitzit nevertheless “pushes off” the prohibition and permits, for example, wool strings on a linen garment.
Aside from the legalistic derivation of aseh docheh lo ta’aseh found in Shas, a fascinating rationale for the principle of aseh docheh lo ta’aseh is found in the writings of the Ramban in his Commentary on the Chumash. He explains that a mitzvah aseh — an act of doing something that Hashem commands — stems from the mitzvah to love Hashem, whereas a mitzvah lo ta’aseh — refraining from an act that Hashem said not to do — stems from the mitzvah to fear Hashem. Since loving Hashem is relatively more important than fearing Him, there is a logical argument for a mitzvah aseh to override and supersede a mitzvah lo ta’aseh. (Of course, any fulfillment of a mitzvah aseh and a non-transgression of a mitzvah lo ta’aseh shows both a great love for Hashem and a great fear and awe of our Creator.)
- Yevamot 5a