1 Now it came to pass, when men began to multiply on the face of the earth, and daughters were born to them,
2 that the sons of God saw the daughters of men, that they were beautiful; and they took wives for themselves of all whom they chose.
3 And the Lord said, “My Spirit shall not strive with man forever, for he is indeed flesh; yet his days shall be one hundred and twenty years.”
4 There were giants on the earth in those days, and also afterward, when the sons of God came in to the daughters of men and they bore children to them. Those were the mighty men who were of old, men of renown.
Some commentators believe that the “sons of God” in verse 2 simply refers to men from the line of Seth who followed God. They believe that these men married women from the line of Cain and their offspring followed their mother’s rejection of God. That view doesn’t make much sense to me. I lean toward Morris’s view as stated below.
The actual phrase bene elohim is used three others times, all in the very ancient book of Job (1:6; 2:1; 38:7). There is no doubt at all that, in these passages, the meaning applies exclusively to the angels. A very similar form (bar elohim) is used in Daniel 3:25, and also refers either to an angel or to a theophany. The term “sons of the mighty” (bene elim) is used in Psalm 29:1 and Psalm 89:6, and again refers to angels. Thus, there seems no reasonable doubt that, in so far as the language itself is concerned, the intent of the writer was to convey the thought of angels—fallen angels, no doubt, since they were acting in opposition to God’s will. …
The reason for questioning this obvious meaning, in addition to the supernaturalistic overtones is (for those who do not reject the idea of angels) the opinion that it would be impossible for angels to have sexual relations with human women and to father children by them. However, this objection presupposes more about angelic abilities than we know. Whenever angels have appeared visibly to men, as recorded in the Bible, they have appeared in the physical bodies of men. …
It is true that the Lord Jesus said that “in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven” (Matthew 22:30). However, this is not equivalent to saying that angels are “sexless,” since people who share in the resurrection will surely retain their own personal identity, whether male or female. Furthermore, angels are always described, when they appear, as “men,” and the pronoun “he” is always used in reference to them. …
When Jesus said that the angels of God in heaven do not marry, this does not necessarily mean that those who have been cast out of heaven were incapable of doing so. It clearly was not God’s will or intention that angels mix in such a way with human women, but these wicked angels were not concerned with obedience to God’s will. In fact, it was probably precisely for the purpose of attempting to thwart God’s will that this particular battalion of the “sons of God” engaged in this illegal invasion of the bodies of the daughters of men. … Desiring to completely corrupt mankind before the promised Seed could accomplish Satan’s defeat, they seem to have decided to utilize the marvelous power of procreation … and to corrupt it to their own ends. — Morris, pages 165-167.
It is significant that the Septuagint renders the phrase “sons of God” as ‘angels of God.” This was the Old Testament version in dominant use in the Apostolic period, and thus this would be the way the phrase would have been read by Christ and His apostles. … This interpretation is strongly implied, and probably required by three New Testament passages: Jude 1:6; 2 Peter 2:4-6; 1 Peter 3:19-20. — Morris, page 168.
A solution seems to consist in recognizing that the children were true human children of truly human fathers and mothers, but that all were possessed and controlled by evil spirits. That is, these fallen angelic “sons of God” accomplished their purposes by something equivalent to demon possession, indwelling the bodies of human men, and then also taking (or “possessing”) the bodies of the women as well. … Thus, the “sons of God” controlled not only the men whose bodies they had acquired for their own exploitation, but also the women they took to themselves in this way, and then all the children they bore. — Morris, page 169.
This particular prophecy [his days shall be a hundred and twenty years v.3] was evidently given … just 120 years before the coming of the Flood. … God has always been long-suffering, even under such awful conditions as prevailed in the days of Noah (1 Peter 3:20). Though all had rejected Him, He still granted 120 years to mankind in light of the bare possibility that at least some might “come to repentance” (2 Peter 3:9). — Morris, page 171.
The children of the unions of the demonically controlled men and women of this period are the ones said to have become the “giants,” the mighty men of old. The word in the Hebrew is nephilim and comes from the verb naphal (“fall”). The natural and probable meaning is “those who have fallen,” probably a reference to the nature of their pseudoparents, the fallen angels. The name came also to mean “giants” and was applied later to the giants seen in Canaan by the Israelite spies (Numbers 13:33). — Morris, page 172.
Wechsler takes a different view.
Resolution in this matter is possible, though it depends, as always, on careful attention to the inseparable interpretative duo of context (the passage’s relationship to the surrounding text, both immediate and canonical) and language (how the passage’s terms and expressions are used elsewhere). Thus, though long-standing and popular, the view that these sons of God in verse 2 are angels who sinned by marrying human women is to be dismissed since it makes no contextual sense—whether in the immediate context of verse 3, in which God’s reaction is exclusively towards man, the slightly larger context of what precedes and follows this episode (i.e., Adam’s genealogy and the Flood, both focused on man, not the angels), or the broader thematic context of Genesis, this first “half” of which represents God’s prosecution of human, not angelic, depravity. Also, the one other occurrence of the term Nephilim, in Numbers 13:33, refers to men of large stature. Nor is there any evidence in Scripture that angels can in fact produce children (see Matthew 22:30) or, even assuming they could, that God would have permitted them such time to marry and produce children before He “cast them into hell and committed them to pits of darkness, reserved for judgment” (2 Peter 2:4). — Wechsler, page 131.
His view is as follows.
These four verses (which in the Hebrew text are not separated into a separate chapter) serve to “fill-out” the foregoing genealogy of 5:1-32 by clearly indicating (here for the first time) that the blessing of begetting offspring was taking place within the general context of marriage—that is, men (the sons of God) “taking” women (the daughters of men) in marriage. The expression “sons of God” should thus be understood, simply, as an idiomatic designation for men—reflecting the creation of man first by God—just as the expression “daughters of men” is clearly intended as an idiomatic designation for women, reflecting the subsequent creation of woman from man. … Unlike any of the other views, it is also consistent with the following statement, expressed by God in response to the activity of verses 1-2 that “My spirit shall not abide in man forever.” … The point of the verse in context is that in response to man’s expanding population, God dramatically limits the duration that the “breath” which he breathed into man (see Genesis 2:7) will abide or remain within him in his depraved state. In other words, as an expression of His mercy and love—not judgment—God here acts to limit the potential expression of human depravity (and hence to limit his potential judgment) by reducing man’s lifespan from the multiple centuries attested in chapter 5 to the proximate duration of 12o years. — Wechsler, page 133-134.
He also believes that Nephilim shouldn’t be translated “giants” but “mighty men,” or literally, “proven warriors.
I’m skeptical. First of all, I think Morris answers all the objections regarding context. I think the verses in Jude and Peter that he quotes offer an explanation for when the angels were imprisoned. Wechsler doesn’t explain why all the similar phrases to Nephilim obviously refer to angels. He doesn’t explain why the offspring of men and women would produce particularly mighty men. I like Morris’s take that the 120 years refer to the time remaining before the Flood (in light of Peter’s reference to that same period). It doesn’t make sense to me that God was saying that man’s lifespan would be 120 years because ever since shortly after the flood, man’s lifespan has been considerably shorter. And a worldwide flood that sent all humans but 8 to a godless eternity in hell doesn’t feel like mercy.
I still lean toward the demon-possessed human men and human women, but I can’t claim a definite understanding of the passage any more than anyone else.