Problem: The phrase “sons of God” is used exclusively in the OT to refer to angels (Job 1:6; 2:1; 38:7). However, the NT informs us that angels “neither marry nor are given in marriage” (Matt. 22:30). Furthermore, if angels married, their children would be half human and half angel. But, angels cannot be redeemed (Heb. 2:14–16; 2 Peter 2:4; Jude 6).
Solution: There are several possible interpretations other than insisting that angels cohabited with humans.
Some Bible scholars believe “sons of God” refers to the godly line of Seth (from whom the redeemer was to come—Gen. 4:26), who intermingled with the godless line of Cain. They point out that (a) this fits the immediate context, (b) it avoids the problems with the angels view, and (c) it accords with the fact that humans are also referred to in the OT as God’s “sons” (Isa. 43:6).
Other scholars believe that “sons of God” refers to great men of old, men of renown. They point to the fact that the text refers to “giants” and “mighty men” (v. 4). This also avoids the problems of angels (spirits) cohabiting with humans.
Still others combine these views and speculate that the “sons of God” were angels who “did not keep their proper domain” (Jude 6) and possessed real human beings, moving them to interbreed with “the daughters of men,” thus producing a superior breed whose offspring were the “giants” and “men of renown.” This view seems to explain all the data without the insuperable problems of angels, who are bodiless (Heb. 1:14) and sexless spirits (Matt. 22:30), cohabiting with humans.