Genesis 6:1-4

Now when humankind began to multiply on the face of the ground and daughters were born to them, then the sons of God saw that the daughters of men were good and they took for themselves wives, any they chose. Then ADONAI said, “My Spirit will not remain with humankind forever, since they are flesh. So their days will be 120 years. The Nephilim were on the earth in those days, and also afterward, whenever the sons of God came to the daughters of men, and gave birth to them. Those were the mighty men of old, men of renown.