Perhaps the most enigmatic figure appearing in Maseches Yevamos is Ben Azzai. In the sugya on peru urevu (63b) he both condemns those who do not fulfill that mitzvah as “ki’ilu shofech damim umema’et hademut,” and is called “na’eh doresh vi’ein na’eh mekayem,” one who cites the halacha without himself following it. What exactly is driving Ben Azzai’s opinion and his exceptional personal practice? Is there any way to reconcile the two?

Several possible approaches present themselves in trying to understand Ben Azzai’s self-exemption from peru urevu. The most basic understanding is one of triage; there are only so many hours in the day, and an hour spent supporting a family’s material and emotional needs is an hour not spent learning Torah. Given this clash, Ben Azzai chooses Torah study over starting a family. A slightly different understanding sees Ben Azzai’s concern not as an issue of time management, but rather one of competing concerns. The emotional energy he would need to expend as a husband and father would conflict with a life fully devoted – mind, body, and soul – to Torah study alone. It would be impossible to properly devote emotional energies to both; inevitably, one or the other would suffer. A third preliminary understanding is that Ben Azzai could not marry because his love was overridingly devoted to Torah, to the point that he could not love a woman. This approach fits well with Ben Azzai’s formulation of “umah e’eseh”, “what should I do”? He did not present his practice as ideal; rather, it was an inevitable reality for him.

However, I believe that an alternative explanation of Ben Azzai’s life choice, viewing it in light of the rules of petur Talmud Torah, affords the best explication of his words, and intertwines with his understanding of peru urevu as well. If we focus on Ben Azzai’s phrase “efshar la’olam sheyitkayem al yedei acheirim,” that his procreation is not integrally necessary since the world can continue without it, a relevant sugya comes into view. The Gemara in Moed Katan (9b) raises contradictory sources as to whether Torah or cheftzei shamayim (i.e. mitzvot) take precedence in one’s personal calculus of observance. The Gemara rules that if a mitzvah can be done al yedei acheirim, by others, Torah takes precedence, while if it cannot, the mitzvah takes precedence. If so, the general rule is that learning gets superseded only for the sake of a mitzvah that cannot be done by others. Of course, this rule does not apply to mitzvot shebigufo. In other words, I cannot expect that someone else will put on tefillin to fulfill my obligation, and therefore I need not stop my learning to put on tefillin. All mitzvot shebigufo fall under the category of cancelling Torah study to fulfill them. One may only skip result-oriented mitzvot such as bikur cholim for learning since others can accomplish them, and there is no need for one to perform the mitzvah himself.

If this is the case, and if Ben Azzai’s statement “efshar la’olam sheyitkayem al yedei acherim” invokes this rule, we can take another look at the conflict between his choice to not marry and his seemingly contradictory position on the dire consequences of not marrying. Ben Azzai claims that not procreating is tantamount to murdering and minimizing the image of Hashem. This is sourced in the pasuk (Bereshis 9:6) “shofech dam haadam baadam damo yishafech ki bitzelem Elokim asa et haadam,” which is directly juxtaposed to “v’atem peru urevu.” As Maharsha explains, this refers to the problem of not increasing the number of lives in the world (equated to murder) and the problem of not increasing the representations of Hashem’s image in the world (equated to minimizing Hashem’s image). If this is the case, then Ben Azzai’s objection to those who do not procreate is not a mitzvah shebigufo but rather a result-oriented mitzvah, a function of how many lives and demuyot exist in the world. Given that it falls into that category, it becomes legitimate for one (including Ben Azzai himself) to invoke the rule of efshar al yedei acheirim. Since others will sufficiently increase the number of lives and representations of Hashem’s image in the world, one can therefore choose to study Torah instead of having children.1

Of course, this understanding of the mitzvah of peru urevu is by no means simple. In fact, it is possible to read this issue as being at the crux of the dispute between Beit Shammai and Beit Hillel as to how many children one is commanded to have. Beit Shammai argues that every man is commanded to have two boys, as Moshe did.2 Beit Hillel on the other hand bases himself on the creation of the world and opines that every man must have a boy and a girl. It is possible to see Beit Shammai’s position as assuming peru urevu is a mitzvah shebigufo, part of the expected duties of a good Jew, as evidenced by the fact that the mekayem hatorah par excellence, Moshe Rabbeinu, had two sons. Beit Hillel sees peru urevu not as a commandment upon the individual, but as part of a broader command to fill the world which devolves upon each man, which is why each male is commanded to father children who emulate the original population of the world, a boy and a girl, and this is also procreation at the approximate replacement rate of society.3 Though this is not the only way to read the basis of the dispute, it does fit very well with Ben Azzai’s position, especially given that we pasken both like Ben Azzai and Beit Hillel, who each say that it is a result-oriented mitzvah rather than a fully personal obligation. May we all merit to fulfill both the mitzvah of Talmud Torah and that of peru urevu to our utmost abilities. 

1 Of course, if one would procreate in addition there would be even more children, the same way that if one also did an act of chesed there would be more chesed accomplished, but the point is that the basic requisite overall continuity/chesed is accomplished.
2 I present the main understandings of Beis Shammai’s and Beis Hillel’s positions, as presented in the mishna. A similar analysis could be carried out for the alternate positions discussed later in the Gemara. 
3 It is possible, but, to my mind, less reasonable, to argue the opposite by each of these cases, that following Moshe is about Moshe fulfilling the result of populating the world, and creation of the world is based on fulfilling an act of imitatio dei, that one has a personal obligation to create a boy and girl just as God did. Additionally, this analysis runs into the interesting question of the relationship between peru urevu and sheves, which seems to clearly be about the result of populating the world.