Genesis 6:1-4

There began to be many human beings on the earth. And daughters were born to them. The sons of God saw that the daughters of human beings were beautiful. So they married any of them they chose. Then the LORD said, “My Spirit will not struggle with human beings forever. They will have only 120 years to live.” The Nephilim were on the earth in those days. That was when the sons of God went to the daughters of human beings. Children were born to them. The Nephilim were famous heroes who lived long ago. Nephilim were also on the earth later on.