We read in Genesis 6:1-4 that, ”When man began to multiply on the face of the land and daughters were born to them, the sons of God saw that the daughters of man were attractive. And they took as their wives any they chose. Then the Lord said, ‘My Spirit shall not abide in man forever, for he is flesh: his days shall be 120 years.’ The Nephilim were on the earth in those days, and also afterward, when the sons of God came in to the daughters of man and they bore children to them. These were the mighty men who were of old, the men of renown.” It is here where we first encounter the word the Hebrew word “Nephilim.” The only other time this word is used is in Numbers 13:33 in the report from the twelve spies. The Greek Septuagint translates this word as “giants” (Greek word “gigantes”). Where the Jewish Publication Society simply transliterated the Hebrew nephilim as "Nephilim," the King James Version translated the term as "giants."
The nature of the Nephilim is complicated by the ambiguity of Genesis 6:4, which leaves it unclear whether they are the "sons of God" or their offspring who are the "mighty men of old, men of renown". Richard Hess in The Anchor Bible Dictionary takes it to mean that the Nephilim are the offspring, as does P. W. Coxon in Dictionary of Deities and Demons in the Bible. I believe that the evidence found by those who are scholars of the ancient Mesopotamian religions universally concur that the Nephilim were the offspring of the “sons of God” and the “daughters of men.”
In addition to the issue of determining the nature of the Nephilim, we have the issue of this term “sons of God.” There are effectively two views: 1) They were the descendants of Seth, 2) They were “angelic” beings. The first view, which is sometimes referred to as the “Sethite” view has had great support in Church history, after the second century. But the second view has the support of orthodox Judaism and many of the earliest Church fathers. It was the apparent view of the rabbis during the Second Temple Period (516 B.C. to 70 A.D.), and seems to be the view of Peter and Jude in their reference to the Book of Enoch (II Peter2:4; Jude 6). The Book of Enoch, which many of the early Church fathers considered as Scripture (Justin Martyr, Irenaeus, Tertullian, Origen) affirms this view.
Other references to the term “sons of God” (Hebrew - ben ha’ Elohim), in the Old Testament, point to them being “angelic” (non-human spiritual beings). For example, Job 1:6, 2:1, 38:7; Deuteronomy 32:8; Psalm 29:1, 89:6; Daniel 3:25. This union of the “sons of God” and the “daughters of men” (Gen.6:2) seems to be something of an extraordinary nature in that it produced “physical” giants.
The Nephilim and Their Descendants
The Nephilim were around before and after the flood. This is confirmed in Numbers 13:33 were we are told that the Anakim at the time of Joshua were the descendants of the Nephilim, meaning that Nephilim were around after the flood in the time of Noah.
There are in my opinion only two possible explanations to account for the continued existence of the Nephilim in the post-flood era. One explanation that the flood in the time of Noah was “regional” and involved the area of the earth where the 70 nations listed in Genesis 10 & 11 inhabited. Therefore, the Nephilim fled to other parts of the earth and escaped judgment. The other possibility is that what occurred in Genesis 6:1-4 occurred again after the flood.
Let me add at this point, that there were Jewish writers who proposed the idea that Noah was fathered by one of the sons of God and was a Nephilim giant. But Genesis 6:9 clearly wants to distance Noah from the unrighteousness that brought about the flood. This explanation is in conflict with the testimony of Scripture itself.
The possibility of a post-flood re-emergence of the Nephilim is not inconsistent with the Hebrew grammar of Genesis 6:4 which states, “The Nephilim were on the earth in those days and also afterward, when the sons of God came in to the daughters of men...”. The “when” in this verse could be translated as “whenever,” thus allowing for a re-occurrence of the pre-flood events. Meaning that “other “sons of God fathered Nephilim after the flood. (The Bible tells us in II Peter 2:4 and Jude 6 the pre-flood sons of God who transgressed are held in “eternal chains” in “Tartarus.”)
In Numbers 13:33, the Nephilim are referred to as the “sons of Anak” and later called the Anakim. The name Anakim, Rephaim, Emim, Zamzummim, Horim, Avvim and possibly Caphtorim all refer to the giants that were called by different names in different locations. (See Deut. 2:10-11, 20-23).
King Og of Bashan is described as “one of the remnant of the Rephaim” whose bed was 13 feet long and made of iron (Deut. 3:11). The Bible speaks of the “Valley of the Rephaim” in Joshua 15:8.
Joshua in conquering Canaan expelled the “descendants of the Nephilim” from the land, except that some took refuge in the Philistine cities of Gaza, Gath, and Ashdod (Joshua 11:22). Goliath and the other Philistine giants whom David encountered (II Sam. 21:15-22) were descendants of the Nephilim.
It is interesting to note that a common belief in the time of Jesus among the rabbis, was that the origin of “demons” was attributed to the events of Genesis 6:1-4. Ancient texts say that when a Nephilim was killed, his disembodied spirit became a “demon.”