Genesis 6:4-6

The Nephilim were in the earth in those days, and also after that, when God’s sons came in to men’s daughters and had children with them. Those were the mighty men who were of old, men of renown. The LORD saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of man’s heart was continually only evil. The LORD was sorry that he had made man on the earth, and it grieved him in his heart.