When mankind’s doom is decided irreversibly, Hashem commands Noach and his family to enter the Ark:
…And you will come to the Ark, you, and your sons, and your wife and your sons’ wives with you (Bereishit 6:18)
As Rashi points out, that this command requires:
The men separately and the women separately.

Noach’s family obeys:
And Noach came with his sons, and his wife and his sons’ wives with him, to the Ark, from before the waters of the Flood (7:7).

Rashi explains that the married couples were commanded to remain celibate during the time that the Flood waters covered the earth. He takes this idea from Bereishit Rabbah 31, 32 and Sanhedrin 108a.

When the earth is dry, Hashem permits them to resume marital life:
Leave the Ark, you and your wife, your sons, and your sons’ wives with you (8:16).
However, they do not return to normal relations yet:
And Noach went out with his sons, and his wife and his sons’ wives with him (8:18).

Bereishit Rabbah explains that they were waiting for Hashem’s blessings, and His assurance that the world would not be destroyed again. After all, Noach’s family was to be responsible for repopulating a destroyed world.

Hashem’s blessing comes after Noach’s sacrifice:
And G-d blessed Noach and his sons, and said to them, “Be fruitful and multiply and fill the earth…And you, be fruitful and multiply, swarm on the earth and multiply on it” (9:1,7).
Rashi (9:7) explains that the first statement is a blessing and the second is a command. And Noach’s sons fulfill this command after the Flood, as we read in chapter 10.

But, why were Noach and his family required to separate in the first place? Malbim takes a practical approach: the population had to be controlled so as to prevent overcrowding and food shortages in the Ark. Indeed, Sanhedrin 108b states that the creatures in the Ark were forbidden to procreate.

The Zohar (Bereishit 204a) says that the Ark was “the tent of Hashem,” where marital relations are inappropriate. Besides, it says, children conceived while the world is cursed would be cursed as well.

However, most commentaries, beginning with Rashi (7:7) say that relations were forbidden “because the world was immersed in sorrow.” As the Talmud (Ta’anit 11a) says
One who pains himself with the community will merit to see the consolation of the community.

It is insufficient to “feel sorry” that others are suffering. A tragedy that strikes the community must be realized and appreciated by all, including those individuals who are spared from the tragedy. One must identify with the community, both in times of joy and in times of sorrow.

Thus, when the Children of Israel fought Amelek (Shemot 17:11-12), Moshe joined them, although he was not a combatant. He raised his hands throughout the battle, since Israel was “immersed in sorrow.” Also, it is recorded that “to Yosef were born two sons before the years of famine” (Bereishit 41:50), because during a famine, one should refrain from marital relations (Rashi). On the other hand, Elimelech is punished for leaving the land of Israel during a famine (Ruth 1:1-3), because he separated himself from the community. One must identify with the misfortunes of the community. Thus, Jewish law requires that, during times of famine, even one who has food should eat sparingly, both in order to share the food with others, as well as to feel the pain of those who have nothing (Shulchan Aruch Orach Chaim 574:4; 240:12).

If a person cannot feel the community’s pain he is not truly a part of the community. As Vladimir Jabotinsky (1881-1940), leader of the Zionist-Revisionists, said: “When you cut a man’s foot and he doesn’t scream, it means that the foot is paralyzed.”

Noach and his family were spared by Hashem from the waters of the Flood because Noach remained a righteous man in a corrupt world. Still, they were a part of that world, and needed to be reminded of this. Hashem teaches Noach: Although the people of the world deserve destruction, and you and your family deserve to be spared, you cannot consider yourselves detached from them; while your community suffers, you must join in their hardship. These survivors were like limbs of a corpus; they were not permitted to feel self-satisfied and turn their backs upon the rest of humankind. They were obligated to share the pain of their human family, if humankind was to deserve to survive. No community is without its faults. Yet, the survival of the community depends on its most righteous members feeling at one with its unrighteous members.

The Jewish community, as well, is a world-wide interdependent body. Some parts of the Jewish world suffer  from poverty, assimilation, anti-Semitism and persecution  while others are safe and prosperous. Jews in the land of Israel are buffeted by international opposition, plagued by terror, burdened by military service. Jews in the Diaspora face uncertainties in identity, the flaring up of hatred, and blistering criticism.

And, throughout the Jewish world, there are more committed Jews and less committed ones, righteous Jews and flawed Jews, Jews of every political stripe and religious perspective. Despite the vast differences, the unity of the Jewish world must be maintained. We are a body, a family. The suffering of some must be felt by all.

It is hard to say, in our present-day world, which of us is “in the ark” and which are “outside the ark”, but we are all in the same boat. Our survival depends on each of us being committed to our unity.