Genesis 6:12

And God looked upon the earth, and, behold, it was
corrupt
This is spoken as if he had never looked upon it before; whereas his eyes are always upon the earth, and the inhabitants of it, and upon all their ways and works: but this denotes the special notice he took, and the particular observation he made upon the condition and circumstances the earth, and its inhabitants, were in. And this is remarked, as well as the particle "behold" is used, to denote the certainty of this corruption; it must needs be true, that the earth was corrupted, since the omniscient God had declared it to be so, who sees and knows all things:

for all flesh had corrupted his way upon the earth:
that is, all men, excepting Noah; who were flesh, carnal and unregenerate persons; these had corrupted the way of God, the true religion, with their idolatries: and they had corrupted their own way, their manners, their life and conversation with their uncleanness and wickedness of various sorts: the Arabic writers ^F25 say, that after Enoch was taken away, the children of Seth and of Cain worshipped idols, everyone as he pleased, and were immersed in wickedness, and gave their right hands to each other, and joined in fellowship in committing sin and vice; and that in the times of Noah, none were left in the holy mount but he and his wife, and his three sons and their wives; all went down below and mixed with the daughters of Cain, and were immersed in sins, and worshipped strange gods, and so the earth was corrupted and filled with lasciviousness. The Jewish writers also observe ^F26, that the generations of Cain were guilty of uncleanness, men and women, like beasts, and defiled themselves with all kind of fornication and incest, everyone with his mother, and with his own sister, and with his brother's wife, and that openly, and in the streets: and Sanchoniatho {a}, the Heathen historian, the writer of the history of Cain's line, says of the fifth generation before the flood, that the women of those times, without shame, lay with any man they could meet with.