Genesis 6:1-3

1 And it came to pass, when men began to multiply on the face of the earth and daughters were born unto them,

2 that the sons of God saw that the daughters of men [were] fair, and they took [for] themselves wives of all whom they chose.

3 And the LORD said, My spirit shall not always strive with man, for certainly he [is] flesh; yet his days shall be one hundred and twenty years.