Genesis 6:4-6 New Revised Standard Version (NRSV)
4 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.
5 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. 6 And the Lord was sorry that he had made humankind on the earth, and it grieved him to his heart.