When people began to multiply on the face of the ground, and daughters were born to them,
the sons of God saw that they were fair; and they took wives for themselves of all that they chose.
Then the Lord said, "My spirit shall not abide in mortals forever, for they are flesh; their days shall be one hundred twenty years."
References for Genesis 6:3
The Nephilim were on the earth in those days—and also afterward—when the sons of God went in to the daughters of humans, who bore children to them. These were the heroes that were of old, warriors of renown.
The Lord saw that the wickedness of humankind was great in the earth, and that every inclination of the thoughts of their hearts was only evil continually.
And the Lord was sorry that he had made humankind on the earth, and it grieved him to his heart.
So the Lord said, "I will blot out from the earth the human beings I have created—people together with animals and creeping things and birds of the air, for I am sorry that I have made them."
But Noah found favor in the sight of the Lord.