1 And it came to pass when the children of men began to multiply on the face of the earth and daughters were born unto them, that the angels of God saw them on a certain year of this jubilee, that they were beautiful to look upon; and they took themselves wives of all whom they chose, and they bare unto them sons and they were giants. 2 And lawlessness increased on the earth and all flesh corrupted its way, alike men and cattle and beasts and birds and everything that walks on the earth -all of them corrupted their ways and their orders, and they began to devour each other, and lawlessness increased on the earth and every imagination of the thoughts of all men (was) thus evil continually.
LXX Genesis 6:2
1 And Noe was five hundred years of age, and Noe became the father of three sons: Sem, Cham, Iapheth. And it came about when humans began to become numerous on the earth, that daughters also were born to them. 2 Now when the angels of God saw the daughters of humans, that they were fair, they took wives for themselves of all that they chose. 3 And the Lord God said, “My spirit shall not abide in these humans forever, because they are flesh, but their days shall be one hundred twenty years.”
Notes and References
"... In common with other Second Temple sources, (Some of the details in Jubilees 5 are strikingly reminiscent of the flood account in 1 Enoch 10-11) Jubilees assumes that the proximate cause of the food was the mating of the “sons of God” with the daughters of men in Genesis 6:1-4. These “sons of God” are, for Jubilees and other interpreters, the angels of the Lord. The offspring born of their union with humans were giants. The identification of these offspring, who are referred to as Nephilim in Genesis 6:4, as “giants” derives from an entirely separate biblical passage, Numbers 13:32-33, wherein some beings “of great stature” are also called Nephilim. Putting these two passages together, ancient interpreters understood the Nephilim in Genesis 6:4 likewise to be of great stature, the giants who resulted from the mating of angels with humans ..."
Kugel, James L. A Walk through Jubilees: Studies in the Book of Jubilees and the World of Its Creation (p. 52) Brill, 2012