Genesis 6:8

And for a very long while wickedness extended and spread, and reached and laid hold upon the whole race of mankind, until a very small seed of righteousness remained among them: and illicit unions took place upon the earth, since angels were united with the daughters of the race of mankind; and they bore to them sons who for their exceeding greatness were called giants.

And then Michael, Uriel, Raphael, and Gabriel looked down from heaven and saw much blood being shed upon the earth, and all lawlessness being wrought upon the earth.

Since the Son of God is always one and the same, He gives to those who believe on Him a well of water [springing up] to eternal life, but He causes the unfruitful fig-tree immediately to dry up; and in the days of Noah He justly brought on the deluge for the purpose of extinguishing that most infamous race of men then existent, who could not bring forth fruit to God, since the angels that sinned had commingled with them, and [acted as He did] in order that He might put a check upon the sins of these men, but [that at the same time] He might preserve the archetype, the formation of Adam. And it was He who rained fire and brimstone from heaven, in the days of Lot, upon Sodom and Gomorrah, "an example of the righteous judgment of God," that all may know, "that every tree that bringeth not forth good fruit shall be cut down, and cast into the fire."

The Scriptures have shown us the gravity of human wickedness and the severity of the punishment that had to be inflicted on it. They then point out to us the one who amid such a multitude had been able to keep a sincere virtue. Virtue in fact is admirable even for itself. If someone cultivates virtue among those who refuse it, he makes it much more worthy of admiration. Therefore the Scriptures, as though in admiration of this just man, point out the contrast: that only one man who was living among those who soon would experience the wrath of God, this Noah, "found favor in the eyes of the Lord God." He "found favor," but "in the eyes of God"; not simply "he found favor" but "in the eyes of the Lord God." This is said in order to show us that he had a single purpose, that is, to be praised by that eye that never sleeps or rests. He had no care for human glory or scorn or irreverence.

Do you see how the Lord created our nature to enjoy free will? I mean, how did it happen, tell me, that while those people showed enthusiasm for wickedness and rendered themselves liable to punishment, this man opted for virtue, shunned association with them and thus felt no effect of punishment? Is it not crystal clear that each person chose wickedness or virtue of his own volition? You see, if that were not the case and freedom did not have its roots in our nature, those people would not have been punished, nor would others receive reward for their virtue. Since, however, everything has been allowed to remain with our choice owing to grace from on high, punishment duly awaits the sinners, and reward and recompense those who practice virtue.