Uno no puede desistir de (la mitzvá de) la procreación a menos que tenga hijos. Beth Shammai dice: Dos varones, [derivado de Moisés, que se separó de su esposa después de haber engendrado dos varones.] Y Beth Hillel dice: Un hombre y una mujer, escrito (Génesis 1:27): "Hombre y mujer los creó ". [Y Moisés no puede servir como precedente, porque actuó por mandato divino.] Si uno se casa con una mujer y vive con ella diez años sin tener hijos, no puede desistir (de la mitzvá). [Como encontramos con Abraham. Después de vivir con Sarah durante diez años y no tener hijos, se casó con Agar. El tiempo que vivió con ella fuera de Eretz Israel no está incluido, ya que vivir fuera de la tierra puede haber contribuido (a su falta de hijos). Y todo el tiempo que un hombre o una mujer están enfermos o encarcelados, o en cualquier otro estado donde se impide la convivencia, esto no está incluido en el período de diez años.] Si se divorcia de ella, se le permite casarse con otro. [Por eso (la falta de hijos) puede deberse no a ella, sino a él. Y cuando se divorcia de ella, le da (la cantidad) de su kethubah, si ella afirma que se debe a que "no disparó como una flecha". Y le imponemos una prohibición si ella sabe lo contrario y hace un reclamo falso contra él.] Al segundo se le permite vivir diez años con ella. Y si ella aborta, él cuenta desde el momento en que ella aborta. La mitzvá de engendrar hijos recae sobre el hombre y no sobre la mujer, [está escrito (Génesis 1:27): "Sé fructífero y multiplícate ... y domínalo" ("vekivshuhah"). Está escrito defectuoso, sin el vav después de la espinilla (lo que implica que solo se está abordando uno y que la mitzvá de la procreación recae sobre el hombre, el "subyugador" de la mujer.)] R. Yochanan b. B'roka dijo: De ambos (hombre y mujer) está escrito (Ibid. 28): "Y Dios los bendijo, y Dios les dijo: 'Sean fructíferos y multiplíquense'" [La halajá no está de acuerdo con él.]
Shadal
And he blessed them: He gave them the power and setup for all of this; and He also said to them, "be fruitful and multiply, etc.," which is to say that He explained to them what their power and nature [consists of] and what He wants from them. And above (verse 22) with the fish and the birds, it did not say "And God said to them," since they are not intelligent creatures. And behold, to man - when the human species was at the beginning of its existence, and so [too] below (Genesis 9:1,7) when the human specie was very little - He explained His desire, that they be fruitful and multiply and fill the earth. And when He gave the Torah to Israel, it was not necessary to command them about this, since the earth was already settled. And nonetheless, the Sages, of blessed memory, did well when they counted (Yevamot 6:6), "be fruitful and multiply" as one of the [Torah's] commandments; since it is certainly the will of God that the human species [continue] to be fruitful and multiply. And especially after the destruction [of the Temple] when the [Jewish] people had decreased, they needed to reinforce this commandment. And 'blessed is He that chose them and their teachings;' since were it not for their prohibitions and their decrees, the nation would have been lost from the world, [just] like several great and powerful nations were lost and forgotten.
ויברך..פרו ורבו, the word הפריה describes the fertilisation, leading up to birth; the word רביה refers to the quantitative development of such offspring. Even though, in the first instance this is a blessing, just as it is in verse 22 when G’d blessed the fish, our sages in Yevamot 65 and in Bereshit Rabbah 8,12 understand this verse as a commandment to the human race to reproduce. They say: “man is command to practice this commandment, whereas for woman it is not an active commandment.” Although the commandment was addressed to man in the plural mode,פרו ורבו, encouraging us to think that the commandment applies to males and females equally, this is not so. As far as the blessing contained in this verse is concerned, it applies to both males and females; the commandment part applies only to the males, and is based on the singular mode in the word וכבשה where the missing letter ו which would have made this a plural mode indicates to our sages that as a directive the whole verse is applicable only to the males of the species. They use psychology to arrive at this conclusion, saying that it is in the nature of the male to engage in conquest, כבוש, not in the mature of the females of the species. Even though this matter is the subject of some disagreement among the sages, (on that folio in Yevamot), the halachah has been decided according to the view that only the male is obligated to fulfill the commandment to have children. The defective spelling of the word וכבשה without the letter ו in the middle, gives rise to additional halachic points, such as that it is not the nature of a woman to go out into the public marketplace, and that the male is to be the instigator of marital intercourse and not his wife. (Bereshit Rabbah 8,12)