Genesis 6:2-4

2the sons of God saw that the daughters of mankind were beautiful, and they took any they chose as wives for themselves.

3And the Lord said, “My Spirit will not remain with mankind forever, because they are corrupt. Their days will be 120 years.”

4The Nephilim were on the earth both in those days and afterward, when the sons of God came to the daughters of mankind, who bore children to them. They were the powerful men of old, the famous men.