Genesis 6:4-6

4The Nephilim were on the earth in those days—and also afterward—when the sons of God went to the daughters of humans and had children by them. They were the heroes of old, men of renown. 5The LORD saw how great the wickedness of the human race had become on the earth, and that every inclination of the thoughts of the human heart was only evil all the time. 6The LORD regretted that he had made human beings on the earth, and his heart was deeply troubled.