Genesis 6:4-6

The Nephilim were on the earth in those days and also later. That was when the sons of God had sexual relations with the daughters of human beings. These women gave birth to children, who became famous and were the mighty warriors of long ago. The LORD saw that the human beings on the earth were very wicked and that everything they thought about was evil. He was sorry he had made human beings on the earth, and his heart was filled with pain.