The Basic Mitzvah
The Mishnah records a dispute concerning the basic parameters of the mitzvah to have children: “A person may not neglect procreation unless he has children. Beis Shamai say: two males; Beis Hillel say: one male and one female, as it says (Bereishis 5): He created them male and female.”
The Gemara explains the rationale for the two positions: “What is the reason for Beis Shamai’s position? We learn from Moshe, as it says (Divrei Ha-Yamim 1:29), ‘The sons of Moshe: Gershom and Eliezer.’ And the reason for Beis Hillel? We learn from the creation of the world. Why does Beis Shamai not learn from the creation of the world? We do not learn what is possible from what is impossible.”
Rashi explains that it was impossible to create the world with only two males, since they could not reproduce. However, now that there is a large population and no lack of women in the world, the mitzvah can be defined as having two sons.
The halachah follows the opinion of Beis Hillel, and one fulfills the mitzvah by having a boy and a girl, thereby emulating Hashem’s creation of the world. The Rambam (Ishus 15:4) thus rules as follows: “How many children must a man have for this commandment to be fulfilled? A male and a female, as it says: ‘male and female he created them.'”
Purpose of the Mitzvah
The Rambam adds a number of important halachos that indicate the idea of continuity that underlies the mitzvah: “If the son or the daughter is not able to procreate, he has not fulfilled the commandment.”
If a person’s children are themselves unable to bear children, he does not fulfill the mitzvah. Moreover, if a person’s children die, he does not fulfill the mitzvah – unless he has grandchildren (15:5):
“If he had children and they died and left children of their own, he has fulfilled the commandment of pirya ve-rivya, since grandchildren are like children. In what situation [is this true]? If the grandchildren are both male and female and they were born to his children who were both male and female. But if he had a son and daughter and they died and one of them left a son and a daughter, then he has still not fulfilled the commandment.”
Although the words recorded in our parashah are spoken to Adam, and not to the Jewish people, the basic rationale of populating the world and preserving the species remains. The Rambam thus writes (Sefer Ha-Mitzvos 212):
“The command which we were commanded to be fruitful and multiply and to intend for the preservation of the species, and this is the commandment of pirya ve-rivya.”
Sefer ha-Hinuch (1) likewise states: “One who violates [peru urvu] has violated a positive commandment and his punishment is very great for he has shown that he does not want to complete G-d’s wishes to populate his world.”
A Passive Mitzvah?
The terminology employed in describing the mitzvah to beget children is unusual. Rather than speaking of a positive action, the Mishnah states the obligation of peru urvu in the negative: “A person may not neglect procreation unless he has children.”
The mitzvah is thus described as the removal of a prohibition (of neglecting procreation) rather than the fulfillment of an obligation.
The Rambam begins his presentation of the mitzvah of peru urvu with a positive instruction: “[A person] is obligated to have relations [on a regular basis] until he has children.” However, the Rambam continues with a passive form that is unique to this mitzvah: “How many children must a man have for this commandment to be fulfilled?”
Following similar lines, the Sefer Ha-Chinuch writes “How many children must he have for him to be exempt,” focusing on the removal of the obligation rather than its fulfillment.
It appears that this terminology derives from the fact that there is no action or sequence of actions which necessarily fulfills peru urvu. The same actions sometimes result in fulfillment, and sometimes do not – the outcome is beyond the ability of man to determine.
Moreover, even one who fulfills peru urvu cannot do so in a conclusive manner, for it is possible that his children will die childless. A person does what he can, and whether or not those actions result in fulfillment remains out of his control. This is perhaps the reason for the unusual terminology used by Chazal and by later authorities in describing the mitzvah.
Indeed, in view of its special nature, authorities dispute the precise definition of the mitzvah.
Mitzvah at Childbirth
Based on the fact that the mitzvah depends on the continued life (and fertility) of a person’s children, the Minchas Chinuch (1:14) writes that the mitzvah of childbearing is essentially different from other mitzvos:
“It seems clear that this mitzvah is not like other mitzvos. The mitzvos of lulav, matzah, and so on, do not have a continued duration. Rather, immediately after performing the mitzvah he has fulfilled his obligation. However, this mitzvah is different, in that the act of procreation is not the mitzvah itself, and is rather a preparation for a mitzvah (hechsher mitzvah), the main part of the mitzvah being actually having children. The obligation is incumbent at every moment, and if the children die a person has not fulfilled his obligation from that time and onward. This is obvious.”
Based on this understanding, the Minchas Chinuch explains the ruling implied by the Rema (Even Ha-Ezer 1:6, based on the Rashba, Yevamos 22b) that the mitzvah of bearing children is fulfilled even with a mamzer child. The simple wording implies that this is true even if the child is the product of a forbidden relationship (the Minchas Chinuch proceeds to question this ruling, and cites sources that dispute it).
Although the general principle is that a mitzvah cannot be performed through a forbidden act, in this case the forbidden act (of marital relations) is not the mitzvah itself, but only a preparation for the mitzvah. The transgression therefore does not affect the fulfillment of the mitzvah.
The Minchas Chinuch further relies on this approach to the mitzvah to explain how it is possible that a convert to Judaism, who had children as a non-Jew and later converted, fulfills the mitzvah with his original children (according to the Rambam this is contingent on their conversion to Judaism) and is not obligated to have children as a Jew.
Although for regular mitzvos this is not the case – a mitzvah performed in a state of halachic exemption from the mitzvah is not a valid performance – the case of peru urvu is different, because the essence of the mitzvah is not the act of procreation, but rather actually having children.
Mitzvah of Marital Relations
The Minchas Chinuch proceeds to point out that an early source – the writings of Tosafos (Bava Basra 13a) – states quite clearly that the mitzvah of peru urvu is fulfilled at the time of marital relations, and not at the time of childbirth. Due to this proof, the Minchas Chinuch leaves the debate as requiring further scrutiny.
Rabbi Moshe Feinstein (Iggros Moshe, Even Ha-Ezer 2:18), however, relies on the implied ruling of Tosafos who reject the position of the Minchas Chinuch:
“It is not logical to believe like the Minchas Chinuch that the mitzvah is not on an action. The essence of the instruction of peru urvu cannot be actually bearing children, because this matter is beyond a person’s control. Rather, the mitzvah and obligation is to have marital relations with his wife, from which it is possible to procreate.”
Based on the above-mentioned Tosafos, and in keeping with the wording of the Mishnah [and the Rambam, as noted above], Rav Moshe explains that the mitzvah involves nothing beyond the act of marital relations, which is in a person’s control. Any later childbirth is not the mitzvah per se, but rather an exemption: Once a person has children, he is no longer obligated in peru uvru.
The Role of Women in the Mitzvah
Although there are minority opinions that maintain that women are included in the obligation of peru urvu (see Yerushalmi, Yevamos 6:6) – just as Chava was included in the original Divine instruction of procreation – the dominant position of the Gemara and of later authorities is that women are exempt from the mitzvah.
This exemption seems odd: Surely women play a central role – the central role, in fact – in childbearing, and if anything, the full brunt of the mitzvah ought to fall on them. What are the reasons behind their exemption?
The Gemara (Yevamos 65b) explains that the verse, “Be fruitful and multiply,” does not apply to women, inasmuch as they are not included in the command at the end of the verse: “Fill the earth and conquer it.” Women are not being commanded here because, as the Gemara explains, “It is in man’s nature to conquer, and not in woman’s nature to conquer.”
It is possible that the deeper understanding of the exemption depends on whether we see the essential mitzvah as being fulfilled in the act of procreation, or by the childbirth.
Rav Ovadiah Bartenoro (commentary to Yevamos 6:6) writes that only a man is obligated to procreate because it is in his nature to ‘subdue’ the woman. Because specifically the man plays the initiating and dominating role in marital relations, it follows that women cannot be obligated in a mitzvah whose path to fulfillment is largely beyond their control.
Rejecting this approach, the Torah Temimah (commentary to Bereishis 1:28) argues that the mitzvah to procreate is part of the larger mandate to conquer and settle the earth (we can add that man is charged with raising the world to the elevation that humanity can bring it), and procreation is essential for achieving this. An exemption from conquering the earth, which does not fit with the female nature, entails an exemption from settling and filling it through childbirth – for the two go together.
A third and novel approach is suggested by Rabbi Meir Simcha of Dvinsk, whose explanation is significantly different. He states (Bereishis 9:7):
“The reason the Torah exempted women from peru urvu and obligated only men, is because G-d’s Law and the Torah’s ways are, “ways of pleasantness and all of her paths are peace” (Mishlei 3:17), and the Torah did not burden a Jew with an obligation that he is physically unable to handle… Therefore, regarding women, who are endangered during pregnancy and childbirth… the Torah did not obligated them to procreate.”
Women, according to this approach, would be obligated in the mitzvah if it did not entail physical danger to them. Because of the risk involved in childbirth, women are exempt from the obligation.
In spite of the exemption, women can still fulfill the mitzvah, as with all mitzvos that a person is exempt from (according to many authorities). In addition, the Ran (Kiddushin 41) writes that women form an integral part of the mitzvah, for without their partnership men would of course be unable to fulfill it.
Moreover, although women are exempt from the Torah obligation of peru urvu, the Tosafos (Gittin 41) explain that they are included in the general instruction to settle the world, which is derived from the verse in Yeshayahu (45:18): “He did not create it [the world] to be empty; He formed it to be inhabited.”

Several contemporary halachic issues are related to the mitzvah of procreation, including such delicate topics as fertility treatments (and the question of fatherhood), surrogacy, contraception, and the general obligation to get married. We will leave these important discussions for a future opportunity.

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