Zohar, Bereshit 47

1R. Jose said: ‘When the descendants of Cain spread through the world, they used to cut up the soil, and they had traits in common both with the upper and the lower beings.’ R. Isaac said: ‘When Uzza and Azael fell from the abode of their sanctity above, they saw the daughters of mankind and sinned with them and begat children. These were the Nefilim (giants), of whom it is said, THE NEFILIM WERE IN THE EARTH (Gen. 6, 4).’

2R. Hiya said: ‘The descendants of Cain were “the sons of God” (Ibid. 2). For Cain was born from Samael and his aspect was not like that of other human beings, and all who came from his stock were called “sons of God”.’

3R. Judah said that the Nefilim were also called so. THE SAME WERE THE MIGHTY MEN. There were sixty on the earth, corresponding to the number above, as it is written, “Threescore mighty men are about it” (S.S. 3, 7). WHICH WERE OF OLD, THE MEN OF NAME. R. Jose saw in the word “name” an indication that they were from the upper world,

4while R. Hiya saw in the word me’olam (“of old” or “from the world”) an indication that they were from the terrestrial world, and that from there God moved them.