Genesis 6:1-4

Now it happened, when men began to multiply on the face of the land, and daughters were born to them, that the sons of God saw that the daughters of men were beautiful and desirable; and they took wives for themselves, whomever they chose and desired. Then the LORD said, “My Spirit shall not strive and remain with man forever, because he is indeed flesh [sinful, corrupt—given over to sensual appetites]; nevertheless his days shall yet be a hundred and twenty years.” There were Nephilim (men of stature, notorious men) on the earth in those days—and also afterward—when the sons of God lived with the daughters of men, and they gave birth to their children. These were the mighty men who were of old, men of renown (great reputation, fame). [Num 13:33]