After the flood, God appeared to Noach and reiterated the command of “peru u-rvu” (“be fruitful and multiply” – 9:7) which had been given to Adam upon his creation, instructing Noach to begin the process of repopulating the earth. God then emphasized, “shirtzu va-aretz” – “swarm the earth.” The Radak explains the term “shirtzu” as a reference to rapid population growth, as indicated by its use in the Torah’s description of Benei Yisrael’s remarkable rate of reproduction in Egypt (“va-yishretzu” – Shemot 1:7). According to the Radak, God emphasized to Noach that he and his children should endeavor to produce a lot of offspring in order to quickly repopulate the newly desolate world.
Rav Shimshon Raphael Hirsch explains differently, noting that the word “sheretz” refers to small insects and the like, the lowest level of living creatures whose existence is defined by nothing more than their movement. As such, Rav Hirsch asserts, the verb “shirtzu” means “swarm,” moving to different locations. In his view, the command “shirtzu va-aretz” instructed Noach and his family to reproduce and to spread across different geographic regions where they would form diverse societies. Rav Hirsch writes:
Noachian mankind is given the mission to spread over the whole world, and under the most diverse conditions and influences of climate and physical nature of the countries, to become Men and develop the one common real character of Man; a diversity and a multiplicity…
God wanted humankind to disperse, to live under drastically different conditions, to show that the principles of morality that people must abide by are relevant and attainable under any condition.
Rav Mordechai Yosef Leiner of Izhbitz, in Mei Ha-shiloach, suggests interpreting the command of “shirtzu va-aretz” based on Rashi’s understanding of the word “sheretz” earlier in Sefer Bereishit (1:20), as referring to very small creatures. Accordingly, the Mei Ha-shiloach finds in the command “shirtzu” a subtle reference to the solution for avoiding the kind of lawlessness that characterized human life during the generation of the flood. The Mei Ha-shiloach explains that God commanded those who came after the flood to live with humility and with humble demands and expectations, to accept “smallness” and feel content even with a modest share. Just as a “sheretz” lives content with its infinitesimally small portion of this earth, we, too, must learn to feel satisfied with whatever we have, without constantly demanding and pursuing more. The turmoil and moral collapse of the generation of the flood resulted from people’s sense of entitlement and greed, their firm belief that they needed and deserved more than they had and more than others had. The antidote to this dangerous mentality is “shirtzu,” living with “small” demands and expectations, recognizing that we can live modestly, that we do not always need more, that we can feel happy and content even if others have a larger share than we do. When we live with this mindset, people can live together peacefully and harmoniously, in mutual respect and consideration.