Genesis 6:3-4

The LORD said, ‘My Spirit will not give life to humans for ever. One day they will die. I will not let them live for more than 120 years. Then they will die.’ The Nephilites lived on the earth at that time, and for some time after that. During that time, the sons of God were having sex with the daughters of men, who gave birth to their children. The Nephilites were famous great men and fighters.