The Torah (Bereishit 1:28, 9:7, 35:11) presents numerous references to the obligation to procreate.  This is known as the mitzvah of p'ru ur'vu.  In this issue, we will discuss the nature and scope of the mitzvah of p'ru ur'vu. 

Is Getting Married a Preparatory Stage for the Mitzvah?

The Gemara, Megillah 27a, states it is permissible to sell a sefer Torah in order to learn Torah or in order to get married.  The Gemara explains that sale of a sefer Torah is permissible in order to get married because the verse (Yeshayahu 45:18) states: "G-d did not create the world for waste, [He created it to be inhabited]."  [See Tosafot, Chagigah 2b, s.v. Lo, who explain why the commandment of p'ru ur'vu was not provided as the reason.]  This implies that the purpose of getting married is for procreation.

Rabbeinu Asher (c. 1250-1327), Ketuvot 1:12, adopts this position and writes that getting married is not a mitzvah but rather a preparatory stage to the mitzvah of p'ru ur'vu.  Based on this position, Rabbeinu Asher writes that the beracha recited together with kiddushin (betrothal) is not a beracha upon performing a mitzvah.   Rather, it is a beracha praising the concept of marriage.  Therefore, it should be recited after the performance of the kiddushin.  Rambam (1138-1204), Hilchot Ishut 1:2, writes that there is a positive commandment to get married.  Rambam, Hilchot Ishut 3:23, also writes that one recites the beracha on kiddushin prior to the performance of kiddushin, consistent with his opinion that there is an inherent mitzvah to get married.

Shulchan Aruch, Even HaEzer 34:1, rules in accordance with Rambam's opinion that one should recite the beracha prior to the performance of kiddushin.  Yet, Shulchan Aruch, Even HaEzer 1:1, writes that one is obligated to get married in order to fulfill the mitzvah of p'ru ur'vu.  Why doesn't Shulchan Aruch write that one is obligated to get married because there is an inherent mitzvah to get married?  Perhaps one can conclude that the opinion of Rambam (and Shulchan Aruch) is that the inherent mitzvah to get married is optional (see Hilchot Ishut 1:1) and it is only because of the mitzvah of p'ru ur'vu that one is obligated to get married.  As such, both Rabbeinu Asher and Rambam agree that getting married is a preparatory stage for the mitzvah of p'ru ur'vu.  They disagree whether there is an additional mitzvah to get married.  

How Does One Fulfill the Mitzvah?

The Mishna, Yevamot 61b, records a dispute between Beit Shammai and Beit Hillel regarding the fulfillment of the mitzvah.  Beit Shammai are of the opinion that one is in fulfillment of the mitzvah if one bears two boys.  Beit Hillel are of the opinion that one is in fulfillment of the mitzvah by bearing a boy and a girl.  While Shulchan Aruch, Even HaEzer 1:5, clearly states that one is not in fulfillment of the mitzvah until one bears a boy and a girl, there are some alternative opinions.  First, R. Chaim Benveniste (1603-1673), Knesset HaGedolah, Even HaEzer, B.Y. 2, suggests that if one's progeny are all of the same gender, and one of those children gives birth to a child of the opposite gender, one is in fulfillment of the mitzvah.  Second, the Talmud Yerushalmi, Yevamot 6:6, records that one can also fulfill the requirement by having two boys.  This leniency is adopted by some Rishonim (see Meiri, Yevamot 61b quoting Gedolei HaDorot, and Teshuvot HaRashba 3:339).

R. Yosef Babad (1801-1874), Minchat Chinuch no. 1, points to two peculiarities regarding this mitzvah that are not apparent in other mitzvot.  First, the Gemara, Yevamot 62a, cites the opinion of R. Yochanan that if one had children and they perished, he is no longer in fulfillment of the mitzvah of p'ru ur'vu.  R. Babad notes that ordinarily, when one fulfills a mitzvah, there is no possibility of forfeiting that fulfillment.  Second, the Gemara, ibid, cites that opinion of R. Yochanan that if a non-Jew had children and then converted, those children may be included to fulfill the mitzvah of p'ru ur'vu.  R. Babad notes that ordinarily, a mitzvah performed by a convert prior to his conversion cannot be counted towards an obligation that must be fulfilled post conversion.  Based on these two peculiarities, R. Babad concludes that the nature of the mitzvah of p'ru ur'vu is different than other mitzvot.  The mitzvah of p'ru ur'vu is not to produce a boy and a girl but rather to be the parent of a boy and a girl.  For this reason, the fulfillment is removed if the children perish.  This also explains how a convert can fulfill the mitzvah by bearing children as a non-Jew.  If the convert is currently the parent of the children, the timing of the action involved in bearing them is insignificant.

R. Moshe Feinstein (1895-1986), Igrot Moshe, Even HaEzer 2:18, disagrees with R. Babad and asserts that the mitzvah of p'ru ur'vu is not result oriented.  The ma'aseh hamitzvah, the action demanded by the mitzvah, is to attempt to produce children through marital relations.  This action itself is the fulfillment of the mitzvah.  The requirement that one bear a boy and a girl does not address the fulfillment of the mitzvah but rather the timeframe of the obligation.  If one is currently the parent of a boy and a girl, there is no obligation of p'ru ur'vu.  If one is not currently the parent of a boy and a girl, there is an obligation of p'ru ur'vu. 

Populating the World

The Gemara, Yevamot 62a-62b, cites a number of opinions that the purpose of the mitzvah of p'ru ur'vu is to populate the world.  This seems to be the basis of the opinion cited in the Gemara, Yevamot 62b, that one who already fulfilled the mitzvah of p'ru ur'vu should continue to have children.

Although the basis for selling a sefer Torah in order to get married is to populate the world, there is a dispute among the Rishonim whether one may sell a sefer Torah when there will be no fulfillment of the mitzvah of p'ru ur'vu.  Tosafot, Yevamot 61b, s.v. Nafka, quote the opinion of Rabbeinu Yitzchak that one may only sell a sefer Torah to get married if one is not in fulfillment of the mitzvah of p'ru ur'vu.  Rabbeinu Asher, Yevamot 6:9, disagrees and maintains that as long as one is planning on populating the world, one may sell a sefer Torah in order to get married.  [See also, Ramban, Milchamot HaShem, Yevamot 20a.]

It is possible that Rabbeinu Yitzchak and Rabbeinu Asher disagree about the relationship between the mitzvah of p'ru ur'vu and its purpose of populating the world.  Rabbeinu Yitzchak is of the opinion that while populating the world has inherent value, the primary method of populating the world is through p'ru ur'vu and that is the only justification to sell a sefer Torah.  Rabbeinu Asher is of the opinion that even when one is not obligated to perform p'ru ur'vu, continued population of the world is an enhanced fulfillment of the mitzvah of p'ru ur'vu.  It is permissible to sell a sefer Torah even to fulfill a non-obligatory aspect of p'ru ur'vu.

The Rishonim allude to another non-obligatory fulfillment of p'ru ur'vu.  The Mishna, Yevamot 65b, states that women are exempt from the mitzvah of p'ru ur'vu.  [See Meshech Chochma, Bereishit 9:7, who explains that the Torah did not want to mandate women to perform a mitzvah that can be very painful and sometimes dangerous to them.]  Tosafot, Gittin 41b, imply that women are also charged with populating the world.  Rabbeinu Nissim (1320-1380), in his responsa (no. 32), writes that although women are not obligated to perform p'ru ur'vu, if they do so, they fulfill the mitzvah.

It is possible to combine the opinions of Tosafot and Rabbeinu Nissim and suggest that if a woman bears children, she fulfills the mitzvah of p'ru ur'vu whose purpose is to populate the world.  This idea is consistent with the opinion of R. Shmuel Feivush (c. 1650-1705) Beit Shmuel, Even HaEzer 1:2, that if one combines Rabbeinu Asher's opinion (that it is permissible to sell a sefer Torah in order to populate the world) with the opinion of Tosafot (that women are also charged with populating the world), one may sell a sefer Torah in order to enable a woman to get married.