Or HaChaim on Genesis 6:13/אור החיים על בראשית ו׳:י״ג

1 ויאמר אלוקים קץ כל בשר, G'd said: "The end of all flesh, etc." If we accept the sages' interpretation that the "violence" mentioned here comprised such sins as bloodshed, incest, and idolatry, we can understand the harshness of the retribution. If however, the word חמס refers to robbery with violence (compare Rashi based on Sanhedrin 108), why would the victims of the robbery suffer the same fate as the perpetrators of the crime?

2Although one might answer that everybody indulged in robbery, each one according to what he thought he could get away with, our sages (Vayikra Rabbah 23,9) have explained the matter differently when they said that in any society in which sexual licentiousness abounds retribution will strike both the wicked and the good people. Therefore we must understand our verse as saying that though the decree to destroy mankind was sealed because of the prevalence of robbery with violence, the fact that amongst all the sins there were many instances of sexual licentiousness and promiscuity resulted in the retribution including also those who were innocent of robbery. You may ask that all these people could have saved themselves from Divine retribution by each one forgiving the other? As a result of this G'd would not have sealed the evil decree! Perhaps G'd did not want to reveal the effectiveness of mutual forgiveness to anyone but Noach. Noach in turn was not able to reveal this secret to his contemporaries seeing that unless G'd tells a person to communicate revelations made to him to others, such revelations are confidential communications from G'd. One of the reasons G'd did not want this secret revealed to Noach's contemporaries may have been that they all remained guilty of having committed robbery. The sin of robbery cannot be atoned for by simply offering the sinner your forgiveness without making restitution. Although the Midrash mentioned types of robbery which are not subject to prosecution, these types of robbery were not the only ones perpetrated by the people of Noach's time. The people of that generation indulged in every form of robbery. Whenever they confronted someone stronger than themselves they resorted to the kind of trickery described by the Midrash. Otherwise they had no qualms about simply grabbing what they fancied.

3The reason G'd explained to Noach exactly what sins prompted Him to decree destruction of the species was to motivate him to build the ark so that all living creatures could be preserved until after the deluge.

4Next we must explain what prompted Noach not to ask G'd to have mercy on the people of his time (as did Abraham when G'd told him He would destroy Sodom). It appears that Abraham learned from Noach not to bother to ask that G'd spare a city when there were fewer than ten good people in it. Unless he had learned this from Noach, who told Abraham that it would be futile to pray for the survival of a city which contained fewer than ten righteous people?

5Noach became convinced from what G'd told him that any prayer of his would be futile, that the fate of these people had been sealed beyond reprieve. All of this is contained in the words: "the end of all flesh has come before Me, here I am about to destroy them." When G'd told Abraham (Genesis 18,20-21) about the sinful nature of the people of Sodom He did not use such kind of language at all. On the contrary, He told Abraham that He was going to examine if what had come to His attention was indeed so, etc. While it is true that in the case of Sodom G'd carried out His decree as soon as He had confirmed the true state of affairs, G'd wanted to demonstrate to Abraham that He does not exercise His power arbitrarily. We have explained in that connection that G'd spoke to Abraham in a manner that invited him to pray on behalf of the doomed cities. Something similar occurred during the episode of the golden calf when G'd proclaimed His intent to wipe out the Jewish people in such a way that Moses saw an opening for his prayer. None of these openings were provided for Noach.

6One cannot argue that if G'd did not want Noach to pray for his contemporaries, He did not have to tell Noach what He was going to do and why. G'd needed to tell Noach in order that the latter build the ark. This commandment alone convinced Noach that it would be useless to pray on behalf of the people. Abraham concluded from the fact that Noach and his family were not enough to save the earth from the deluge that fewer than ten good people could not save a town from destruction.