There are two events in the Torah that can be identified as yeshu'os, by which I mean events where Hashem saved someone even though they didn't really merit it.
The more obvious is Yetzi'as Mitzrayim, the Exodus. Hashem saved us just as we were slipping from the "49th level of impurity" into being hopelessly corrupt. And in the introduction before Az Yashir, the song by the Red Sea, we are told that "Vayosha' Hashem... -- and Hashem saved on that day Israel from the hands of Egypt..." (Shemos 14:30)
An earlier example is when Hashem saved Lot and his family from the destruction of Sodom. There too Lot was saved primarily in Avraham's merit, that Avraham should be spared the pain of losing his nephew.
There is a common feature in these two stories. The ones being saved are restrained from rejoicing over the fall of those who were not. I would suggest that this is a property of yeshu'ah. Without the element of witnessing divine justice, there is no justification for reveling in the fall of the wicked. And here the potential witness was saved by Hashem's mercy, justice isn't in evidence.
Among the reasons the gemara (Megillah 14a) gives us for why we do not recite full Hallel on the last day(s) of Pesach is a medrash about G-d's discontent with the angels joining in our singing Az Yashir. "The work of My 'Hands' are drowning in the sea, and you sing?" The day we crossed the sea is not to be one of unrestrained joy. Note that we do not have a similar muting of the joy of Chanukah, despite the deaths of the Saleucids and Hellenized Jews. The Exodus, however, was a yeshu'ah.
With Lot this point is particularly stressed. Lot was told not even to look back at the destruction. His wife was turned into salt for trying to do so.
What about Noach? Was his a yeshu'ah, or did he earn being saved?
There is a famous Rashi on the words of the first verse of this week's parashah. "Noach was a wholehearted man in his generation." (Ber' 6:9) Rashi notes two interpretations of this comment. On the one hand, it could be taken as a compliment of Noach. Even in the environment and culture of Noach's contemporaries, he was still a good person. Alternatively, it could be taken as a criticism. By the low expectations of that period, he was a good man. But had he lived in Avraham's day, he would have been a nobody.
There is another debate recorded in Rashi that also touches on our question. In (6:16) Noach is told to make a tzohar for the ark. Rashi quotes Bereishis Raba, and again there are two positions. One defines "tzohar" to be a window, the other a gem.
I would like to suggest that these two Rashis are recording different aspects of the same disagreement. According to the first position, we look at Noach in terms of the relative scale of his potential. Noach did an excellent job, given what he had to work with. In that light, he merited being saved. Therefore, Noach was not in the position of Lot, he was allowed to see what transpired to his peers. Therefore, this tanna would have no problem saying that the ark had a window through which Noach could see out.
The second looks at him in an absolute scale. By that standard, he didn't get as far. His salvation would therefore be seen as an act of Divine Mercy, a yeshu'ah. So to this opinion, the tzohar couldn't have been a window. It was a gem that obscured his view.
After Noach left the ark, Hashem made a covenant with him. Hashem gave Noach seven mitzvos for all of humanity to observe and promised Noach that He would never again flood the entire world.
There are two seemingly contradictory halachos about rainbows. The first is that we make a berachah of thanks when seeing a rainbow (Berachos 59a). On the other hand, we are told not to gaze at a rainbow because it's a sign of Divine Anger, that G-d is telling us that it's only his promise to Noach that keeps Him from again flooding the world. (Chagiga 16a)
There is another difference between having the light come into the ark via a window or a gem. Light that comes in through a cut stone will be refracted. The inside walls of the ark would have been covered with little rainbows.
Perhaps this is another reason why G-d chose the rainbow to be the sign of his covenant with Noach. The rainbow reminds us that the world is our "ark" by painting a similar spectrum on our "walls". The sign of the rainbow is therefore that of a yeshu'ah, of unmerited salvation. For which we should be thankful, but not proud.© 2001 The AishDas Society