Genesis 6:1-4

¶ And it came to pass, when men began to multiply on the face of the earth and daughters were born unto them, that the sons of God saw that the daughters of men were fair, and they took for themselves wives of all whom they chose. ¶ 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. ¶ There were giants in the earth in those days, and also after that, when the sons of God came in unto the daughters of men, and they bore sons to them, the same became mighty men who were of old, men of renown.