By Crosswalk Editorial, Crosswalk.com
"When human beings began to increase in number on the earth and daughters were born to them, the sons of God saw that the daughters of humans were beautiful, and they married any of them they chose. Then the LORD said, “My Spirit will not contend with humans forever, for they are mortal ; their days will be a hundred and twenty years.” The Nephilim were on the earth in those days—and also afterward—when the sons of God went to the daughters of humans and had children by them. They were the heroes of old, men of renown."
It is actually plausible the Nephilim were partly both fallen angels and giants. According to Genesis 6:1-4, the Nephilim were the children of the relations between the sons of God and daughters of men. Christian scholars have theorized that the “sons of God” were fallen angels (demons) who reproduced with human females or possessed human males who then bore children with human females. Being the offspring of partial angelic heredity, the Nephilim were considered "mighty men who were of old, the men of renown."
Why would fallen angels reproduce with humans? As to a clear motive, one consideration is that the fallen angels, or demons, were trying to distort the human lineage in order to stop the arrival of the Messiah. God had assured mankind that the Messiah would one day "crush the head" of Satan (Genesis 3:15). The fallen sons of God in Genesis 6 were perhaps seeking to prevent this and make it impossible for an innocent “seed of the woman” to be born.
The Nephilim in Theology
According to Hebrew doctrine like the Book of Enoch, the Nephilim were a breed of giants and super-humans who performed deeds of exceptional evil. Their large size and power probably came from the merger of (fallen) angelic “DNA” with human eugenics. There are actually only two explicit references to the Nephilim in the Biblical text. First in Genesis 6:4, "The Nephilim were on the earth in those days—and also afterward—when the sons of God went to the daughters of humans and had children by them. They were the heroes of old, men of renown." And second in Numbers 13:33, "We saw the Nephilim there (the descendants of Anak come from the Nephilim). We seemed like grasshoppers in our own eyes, and we looked the same to them.”
The Nephilim and the Great Flood
It is speculated by Christian scholars that the Nephilim were one of the main causes for the great flood in Noah’s era. Promptly after the reference of Nephilim, Genesis 6:5-7 states, “The LORD saw how great man’s wickedness on the earth had become, and that every inclination of the thoughts of his heart was only evil all the time. The LORD was grieved that he had made man on the earth, and his heart was filled with pain. So the LORD said, ‘I will wipe mankind, whom I have created, from the face of the earth—men and animals, and creatures that move along the ground, and birds of the air—for I am grieved that I have made them’”. God then flooded the whole earth, killing everyone and everything other than Noah, his family, and the animals on the ark. All else died, even the Nephilim.
Were the Nephilim in the Land of Canaan?
Although the great flood in Genesis killed the Nephilim of that time, it is theorized that the demons continued their breeding with humans sometime after the flood as well. After the Hebrews scouted the land of Canaan, they told Moses: “We saw the Nephilim there (the descendants of Anak come from the Nephilim). We seemed like grasshoppers in our own eyes, and we looked the same to them”. This scripture quote does not mention the Nephilim were actually there, only that the scouts believed they had seen the Nephilim. It is possible that they simply observed abnormally large people in Canaan and in fear thought them to be the Nephilim. Either way, these “giants” were defeated by the Israelites through their conquering of Canaan (Joshua 11:21-22).
Could the Nephilim Return?
According to scripture, God has stopped fallen angels from mating with humans by banishing all those who performed such an act to darkness. Jude 1:6 informs us, “The angels who did not keep their positions of authority but abandoned their own home—these he has kept in darkness, bound with everlasting chains for judgment on the great Day.” It is presumed that fallen angels who bred with human females are the ones who are “bound with everlasting chains" making the return of Nephilim thankfully unlikely.