Gen 6:4
“The Nephilim were on the earth in those days, and also after that, when the sons of God came in unto the daughters of men, and they bare children to them: these are the heroes (הגּבּרים) who from the olden time (מעולם, as in Psa 25:6; 1Sa 27:8) are the men of name” (i.e., noted, renowned or notorious men). נפילים, from נפל to fall upon (Job 1:15; Jos 11:7), signifies the invaders (ἐπιπίπτοντες Aq., βιαῖοι Sym.). Luther gives the correct meaning, “tyrants:” they were called Nephilim because they fell upon the people and oppressed them.
The meaning of the verse is a subject of dispute. To an unprejudiced mind, the words, as they stand, represent the Nephilim, who were on the earth in those days, as existing before the sons of God began to marry the daughters of men, and clearly distinguish them from the fruits of these marriages. היוּ can no more be rendered “they became, or arose,” in this connection, than היה in Gen 1:2. ויּהיוּ would have been the proper word. The expression “in those days” refers most naturally to the time when God pronounced the sentence upon the degenerate race; but it is so general and comprehensive a term, that it must not be confined exclusively to that time, not merely because the divine sentence was first pronounced after these marriages were contracted, and the marriages, if they did not produce the corruption, raised it to that fulness of iniquity which was ripe for the judgment, but still more because the words “after that” represent the marriages which drew down the judgment as an event that followed the appearance of the Nephilim. “The same were mighty men:” this might point back to the Nephilim; but it is a more natural supposition, that it refers to the children born to the sons of God. “These,” i.e., the sons sprung from those marriages, “are the heroes, those renowned heroes of old.”
Now if, according to the simple meaning of the passage, the Nephilim were in existence at the very time when the sons of God came in to the daughters of men, the appearance of the Nephilim cannot afford the slightest evidence that the “sons of God” were angels, by whom a family of monsters were begotten, whether demigods, daemons, or angel-men.