Genesis 6:1-4

People started to increase in number and spread out across the earth. Daughters were born to them, and the sons of God saw that these women were beautiful, and they took whichever ones they wanted. Then the Lord said, “My life-giving Spirit will not remain in these people forever, because they are only mortal. The time they have left will be 120 years.” There were giants on earth in those days, and also later on. They were born after the sons of God slept with the daughters of these people. Their sons became the great warriors and famous men of ancient times.