Мусар к Берешит 9:1

The author quotes Rabbi Eliyahu Mizrachi, who addresses himself to that difficulty in his commentary on Rashi and opines that both in Genesis 1,28 and 9,1 the Torah expresses a blessing which subsequently is followed by the words פרו ורבו as a commandment. The latter statement is to be understood as an elaboration of the blessing. The actual commandment however is derived only from Genesis 9,7: ואתם פרו ורבו. This sentence does not contain a blessing and is in agreement with the statement in Sanhedrin 59.

According to this, the homiletical meaning Rashi speaks about, namely the comparison of someone who fails to carry out that commandment to a murderer as stated by Rabbi Eliezer in Yevamot 63, is based on the verse immediately prior to that in which the Torah proclaims: שופך דם האדם באדם דמו ישפך, "Whoever sheds the blood of man, by man shall his blood be shed." He apparently holds that only males are commanded to fulfil this commandment, and disagrees with Rabbi Yochanan ben Broka. The latter holds that the line "He blessed them," applied to both man and woman. The reason that the other scholar disagrees is that he holds that just as only males are in the habit of conquering, a condition in Genesis 1,28, so only males have to fulfil the condition of being fruitful. Clearly then he must hold that the words "He said to them, etc." must be understood as a commandment. The same reasoning applies to the first time the words פרו ורבו appear in Genesis 9,1. Rabbi Yochanan would then be in disagreement with Bar Kappara and the Talmud Sanhedrin 59, who both hold that the commandment is only found in Genesis 9,7, i.e. ואתם פרו ורבו. Nonetheless he interprets these verses homiletically on the basis of Rabbi Eliezer who believes that a homiletical explanation based on matters which appear side by side in the Torah is almost a commandment in itself [words are mine. Ed.]. Rabbi Eliezer bases his approach to exegesis on Psalms 111,8: סמוכים לעד לעולם, that words next to one another always, i.e. under all conditions, have an exegetical significance. Rabbi Eliezer applies that principle even when the verses in question are not "free" for homiletics but have already been explained as necessary in a different context.

Rabbi Eliyahu Mizrachi also quotes Nachmanides in his comment on Rashi who claims that the homiletics Rashi mentions only tell us not to apply the principle of סמוכים, i.e. that subject matter that is mentioned side by side must have halachic consequences. He too views the first פרו ורבו in 9,1 as a blessing and derives the commandment only from this latter ואתם פרו ורבו. He sees in the additional words שרצו בארץ an exhortation to be extremely fruitful so that the earth may be populated all over. Rabbi Mizrachi does not agree with the position taken by Nachmanides, and argues that the Midrash quoted by Rashi may well be in agreement with the opinion of the Talmud as expressed in Yevamot, and that the word ורבו, even though it is introduced by the words ויברך both here and in Parshat Bereshit, are not part of the blessing but constitute a separate commandment. The latter verse (9,7) only serves to establish the comparison with the preceding verse, namely that failure to procreate is a mortal sin. The reason that this verse is necessary is that Rashi agrees with Rabbi Yehudah who does not employ סמוכים, (verses that are following one another but dealing with separate subject matters) as a basis for halachic exegesis -unless such verses cannot be explained otherwise. He also disputes that one could interpret the verse in פרשת בראשית as introducing a commandment, whereas the similar verse in 9,1 would only be a blessing.