It is written: "And Adam lived a hundred and thirty years, and he begot a son in his likeness, after his image" (Genesis 5:3). From here you learn that Cain was not of the seed, nor of the likeness, nor of the image of Adam, and his deeds were not like the deeds of Abel his brother, until Seth was born, who was of his seed and his likeness, and his deeds were like the deeds of Abel his brother, as it is said: "And he begot a son in his likeness, after his image" (Genesis 5:3). Rabbi Ishmael says: From Seth there arose and were traced all the creatures and all the generations of the righteous, and from Cain there arose and were traced all the generations of the wicked, the transgressors, and the rebels, who rebelled against the Omnipresent and said: "We have no need of the drop of Your rains, nor to know Your ways," as it is said: "And they said to God: Depart from us" (Job 21:14). Rabbi Meir says: The generations of Cain went about with their nakedness uncovered, the men and the women like cattle, and they defiled themselves with every kind of harlotry, a man with his mother and his daughter and his brother's wife, uncovering themselves in the streets with the evil inclination and with the thoughts of their heart, as it is said: "And the LORD saw that the wickedness of man was great upon the earth" (Genesis 6:5). Rabbi says: The angels who had fallen from their place of holiness in heaven saw the daughters of Cain walking about with their nakedness uncovered and painting their eyes like harlots, and they went astray after them and took wives from among them, as it is said: "And the sons of God saw the daughters of man" (Genesis 6:2), and so forth. Rabbi Yehoshua ben Korhah says: The angels are flaming fire, as it is said: "His ministers a flaming fire" (Psalms 104:4), and how does fire come in copulation with flesh and blood and not burn the body? Rather, at the hour when they fell from heaven, from their place of holiness, their strength and their stature were like the sons of man, and their garment was a clod of dust, as it is said: "My flesh is clothed with worms and a clod of dust" (Job 7:5). Rabbi Tzadok says: From them were born the giants who walk about with lofty stature, and stretch out their hand in every robbery and violence and shedding of blood, as it is written: "And there we saw the Nephilim" (Numbers 13:33), and so forth, and it says: "The Nephilim were on the earth" (Genesis 6:4). Rabbi Yehoshua ben Korhah said: Israel are called sons of God, as it is said: "When the morning stars sang together and all the sons of God shouted for joy" (Job 38:7). And these, while they were in their place of holiness in heaven, were called sons of God, as it is said: "And also after that, when the sons of God came in" (Genesis 6:4). Rabbi Levi says: They begot their children and were fruitful and multiplied like a great swarming creature, six at every birth. At that very hour they would stand upon their feet and speak in the holy tongue and dance before them, as it is said: "They send forth their little ones like a flock" (Job 21:11). Noah said to them: "Turn back from your ways and from your evil deeds, lest the waters of the Flood come upon you and cut off all the seed of the sons of man." They said to him: "Behold, we restrain ourselves from being fruitful and multiplying, so as not to bring forth the seed of the sons of man." What did they do? When they came to their wives, they would destroy the source of their seed upon the ground, so as not to bring forth the seed of the sons of man, as it is said: "And God saw the earth, and behold, it was corrupt" (Genesis 6:12). They said: "If the waters of the Flood come upon us, behold, we are of lofty stature and the waters will not reach as high as our necks; and if He brings up the waters of the deeps upon us, behold, the soles of our feet can stop up the deeps." What did they do? They spread out the soles of their feet and stopped up all the deeps. What did the Holy One, blessed be He, do? He made the waters of the deeps boil, and they scalded their flesh and stripped their skin from off them, as it is said: "In the time they grow warm they are scorched; when it is hot they are extinguished from their place" (Job 6:17). Do not read "in its heat" but "in its hot water."