And the LORD said, My spirit shall not always strive with man, for that he also is flesh: yet his days shall be a hundred and twenty years.
All Commentaries on Genesis 6:3 Go To Genesis 6
Augustine of Hippo
By the justice of God the whole human race was delivered into the power of the devil, the sin of the first man passing originally into all persons of both sexes, who were born through conjugal union, the debt of our first parents binding all their posterity. This delivering was first indicated in Genesis, where, when it was said to the serpent, “Earth shall you eat,” it was said to the man, “Earth you are, and into earth shall you return.” The death of the body was foretold by “into earth shall you return,” because he would not have experienced it if he had remained upright as he had been created. But what he says to the living man, “earth you are,” shows that the whole man has been changed into something worse, for “earth you are” is just the same as saying “My spirit shall not remain in those men, because they are flesh.” Hence God showed that he had then delivered man to the devil, to whom he had said, “Earth shall you eat.” .