This week's section, Noah, tells the story of the flood. In short, all of humanity had become corrupt, as had many animal species, so God decided to "wipe out" (see Genesis 6:7) everyone except Noah and his family, along with those animals that had not become corrupt.
And from there to the well-known story of the Ark, the flood, rain for forty days and forty nights, the entire world completely inundated for a year. Then the water gradually recedes and evaporates completely, the Ark comes to rest on Mount Ararat (northeast Turkey), and Noah, along with his family and all the animals from the Ark, leave it and populate the earth.
After Noah makes a series of offerings, God makes a covenant with him, swearing that He will never again bring a flood upon the earth. This covenant is sealed with a sign: the rainbow.
(Rabbi Moshe ben Nachman (1194-1270) explains that before the flood, the clouds (and the earth in general) did not have a state of refinement that allowed them to reflect sunlight to form the rainbow, and only after the flood was there a certain purity and refinement that made it possible to see the rainbow from then on.)
The Torah relates that if God were to consider wiping humanity out once more (because of its evil deeds), when He sees the rainbow, He will remember the covenant He made with Noah, not to send another flood to destroy everyone. In fact, there were generations in human history when the rainbow was never seen, such as the generation of King Hezekiah, or that of the sage Rabbi Shimon bar Yochai, who, having possessed such great merit, made the rainbow unnecessary, since in their time, God never considered wiping humanity out.
Now, this portion of history challenges us to consider where we stand: are we a generation that doesn't see the rainbow? The truth is, no, but that doesn't mean we lack the capacity to perform good deeds. In other words, the Talmud mentions a few generations where the rainbow wasn't necessary, implying that it was for the rest. We are no less than them in that sense, and moreover, we are the generation whose task is to prepare for the imminent arrival of the Messiah. Based on and supported by the millennia-old work of our ancestors, we are the ones who, in practice, can capitalize on all their efforts and bring about that long-awaited Redemption.
We simply need to accept the challenge and know that the next time the rainbow appears, the right attitude is to work even harder and increase our connection with God through the Torah and the Mitzvot.