Genesis 6:4
1 When humankind began to multiply on the face of the earth, and daughters were born to them, 2 the sons of God saw that the daughters of humankind were beautiful. Thus they took wives for themselves from any they chose. 3 So the Lord said, “My Spirit will not remain in humankind indefinitely, since they are mortal. They will remain for 120 more years.” 4 The Nephilim were on the earth in those days (and also after this) when the sons of God would sleep with the daughters of humankind, who gave birth to their children. They were the mighty heroes of old, the famous men. 5 But the Lord saw that the wickedness of humankind had become great on the earth. Every inclination of the thoughts of their minds was only evil all the time. 6 The Lord regretted that he had made humankind on the earth, and he was highly offended.
Numbers 13:33
31 But the men who had gone up with him said, “We are not able to go up against these people, because they are stronger than we are!” 32 Then they presented the Israelites with a discouraging report of the land they had investigated, saying, “The land that we passed through to investigate is a land that devours its inhabitants. All the people we saw there are of great stature. 33 We even saw the Nephilim there (the descendants of Anak came from the Nephilim), and we seemed like grasshoppers both to ourselves and to them.”
Notes and References
"... The specific correlation between the Nephilim in Numbers 13:33 and “the sons of Anak” (verses 22, 28) would have widened the horizon for ancient readers to have inferred links between groups of various names within the biblical tradition, whether in the Masoretic text or the LXX tradition. For example, in Deuteronomy 2:10–11 an apparent gloss refers to inhabitants of Ar called “the Emim … a great and numerous and tall people” who “like the Anakim are thought to be the Rephaim” (see also verses 20–21). The correspondence chain of Giborim = Nephilim = Anakim = Rephaim, which could be inferred from reading synthetically the Hebrew of Genesis 6, Numbers 13, and Deuteronomy 2, is consistent with a translation strategy in the Greek tradition that often applied, as we have seen above, the term γίγας ('giants'), for these words. By implication, Og king of Bashan could have been related to this circle, as may be suggested by the gloss at Deuteronomy 3:11 (see also 3:13) about the unusually large size of his bed and the claim that he “alone was left remaining from the remnant of the Rephaim (מיתררפאים)” ..."
Stuckenbruck, Loren T. The Myth of Rebellious Angels: Studies in Second Temple Judaism and New Testament Texts (p. 6) Mohr Siebeck, 2014
"... The Nephilim were last mentioned in a J text (Genesis 6:4), which identifies them as giants, the offspring of human women and “the sons of God.” Now they are found living in the land. Later (in a J text in Joshua), Joshua eliminates the giants from all the land except the city of Gath and two other Philistine cities (Joshua 11:21-22). And later still, the famous Philistine giant Goliath comes from Gath (in 1 Samuel 17:4, a text identified in The Hidden Book in the Bible as having been written by the same author as J) ..."
Friedman, Richard Elliott The Bible with Sources Revealed: A New View Into the Five Books of Moses (p. 263) Harper San Francisco, 2005